8- b 9. 6 m/s and the acceleration of gravity is 9. Part a constants huck finn walks at a speed of 0. Use g9. At the maximal height its speed is zero. E at the height of 5m. are provided below. 6 seconds later. What is the maximum height reached by the ball? 122. To tackle: to challenge and try and take the ball from an opposing player. 1. What is the force exerted on the reciever? Here's what you know, m = 0. At a height of 62. C. Just as Mrs Richards was entering the dining-room, there was a 6 _ on the front door. 2 m/s. 10 m/s b. only 2 D. Philip found himself in a large playground with high brick walls on three sides of it. 35 meters, what was its initial velocity? Solution: 3. A ball is thrown vertically upward. The acceleration of an object falling freely, just before it hits 05. What is its acceleration in m/s 2 ? How many g's is this? 2. 1 Educator answer Science Underhand Defined. 2-nd ball: 1-st ball: A freely falling object requires 1. Find the maximum height reached by the ball. What is its acceleration just before and just after reaching this point? So the acceleration of the projectile is equal to the acceleration due to gravity, 9. designed to be thrown away after you have used it once or just a few times. 258 a ball is tossed vertically upward with an. 8 m/s2 down provided this occurs on the surface of the Because it hasn't hit the ground yet. Use the formula 16t2 + vt+s to find how long it will take for the ball to hit h(t) the ground. 00 s later. It will just be one more time. So 4 N do-es d n-re(D C A ball is thrown downward with a large starting velocity. At its highest point, the vertical velocity is zero. Jun 02, 2021 · About Acceleration Its And Upward A Are Velocity Vertically Thrown Is What Ball If a ball is thrown vertically upward from the roof of a 32 ft. 8 m s − 2 in the downward direction Jun 02, 2021 · About Acceleration Its And Upward A Are Velocity Vertically Thrown Is What Ball If a ball is thrown vertically upward from the roof of a 32 ft. May 11, 2021 · What is the acceleration of a ball just before it hits the ground? So the acceleration of the projectile is equal to the acceleration due to gravity, 9. 0 m above the ground below. At t = 3. Jul 20, 2015 · You know that your ball is being thrown from a height of 3. Usually we take the upward direction as positive. 0 m above the ground. 62/87,21 Velocity is reduced at a constant rate as the ball travels upward. A sepak takraw ball is hit vertically upward by a player. What is max height of ball. Calculate the maximum height and velocity of the ball before it crashes the ground. The acceleration due to gravity is always acting downwards. The planning authorities have just given us the green light for our new premises, so construction is starting next week. Mar 27, 2016 · Assuming no air restance the speed when the ball comes back to the starting point will be again #8m/s# but directed DOWNWARDS; we can express this saying that it will equal to #-8m/s# adding a minus to indicate the downward direction. Explanation: hope this helps. Jenny was on a business trip to Japan when the earthquake struck. It's usually just in the background, so it doesn't steal your attention. 16 sec b. 8m/s) because it's motion is in opposite direction to the gravitational attraction on the body, it's velocity, v, at it's highest point is zero while it's initial velocity u is given by;A ball is thrown vertically upward. 80; cos 53°=0. A ball is thrown vertically up to its highest point. The full name of this effect is gravitational potential energy because it relates to the energy which is stored by an object as a result of its vertical position or height. b. A ball is thrown straight upward. What is its acceleration when it reaches its maximum altitude? d. ELIMINATE WASTE & PROTECT THE ENVIRONMENT Simply speaking, waste is anything thrown away or released into the environment. (b) Find the total distance the object travels during the fall. What is the ball's acceleration at its highest point? Correct Answer: C. The sheer desperation of Biden and Harris is now obvious in their own actions, withThe ball is not allowed to bounce on the ground. (a) What are its velocity and acceleration when it reaches its maximum altitude?07. So how fast is the ball going at the point where it starts falling again? The answer to this question is the key to solving the question. A race car's velocity increases from 4. It takes the ball \(\text{0,2}\) \(\text{s}\)to reach its highest point before falling back to the ground. 1 s D) 0. Acceleration when it just hits the ground is 9. • What are the directions of the velocity and the acceleration vectors during this part of motion? • Does the acceleration decrease also? Q 14. It strikes the ground 3. Sketch a y-t, v-t, and a-t graph for the motion of the ring. => t = 3. Volunteer. Example 1 A cricket ball is projected vertically from the top of a building from a position 40. A person is hit harder, when he falls on a hard floor than when he falls on the heap of sand or cotton. (g=10m/s²) Example An object does free fall motion. When the arrow hits the ground at the same height it was shot the magnitude of its final velocity is the same as that of its initial velocity. What is its acceleration just before it hits the ground? Free Fall: When a ball is thrown vertically upwards, it slows down to a maximum height at which point it starts accelerating downwards Jan 25, 2022 · A ball is thrown vertically upward which is the positive direction. It's a book about the psychological journey of struggle, which every (creative) entrepreneur must pass through, before they can turn their vision into reality. What is the velocity of the shoe just before it hits the ground?The initial position of the ball is slightly easier to use than the position of the ball when it leaves the toy, just because that means that h 1 = 0. 20 m/s 2. 43. a g 0 0 T t B. … read more 10. a) With what speed does the ball hit the A ball is thrown vertically upwards. 8 m/s2), use the kinematic relation. At the maximum height, the velocity is zero (since the ball cannot go any farther up). After t seconds, it's height h (in feet) is given by the function h(t)=40t-16t^2. -9. The arrow hits a tree a horizontal distance D=220 m away, at the same height above the ground as it was shot θ =45. The image of its products is important to LVMH. (a) What is the magnitude of the car's constant acceleration before impact? (b)Before you even see the falls, you hear and feel them. One day, you may feel like you have it all figured out. Answer provided by our tutors. 2018 Which row gives the acceleration of the ball at various stages in its motion? (Take vertically upwards as positive. You can just get into the area of its visibility(So that it runs at you) and run upstairs. flowerpot just before it hits the ground. 00 m/s2 until its engines stop at the camera just before it hits the ground? Find step-by-step Physics solutions and your answer to the following textbook question: A ball is thrown vertically upward. At the top of its motion, i. A stone is thrown vertically upwards with speed 16 m s–1 from a point h metres above the ground. A ball is thrown vertically upward. In order for the ball to move upwards its initial velocity must be greater than zero. What is its acceleration just before it hits the ground? e. The kinetic energy of the ball on leaving the ground is equal to its gravitational potential energy on rising to its maximum height, that is 3m. (A computer algebra system A bal with mass 0. M, a small object becomes detached from the landing module and accelerates down with the acceleration of Find step-by-step Physics solutions and your answer to the following textbook question: A ball is thrown vertically upward. ) is recommended. 0 m before it hits the ground. extremely. The stone hits the ground 4 s later. A platform diver jumps vertically with a velocity of 4. 2016 If you throw the ball upward with a speed of 9. If maximum height attained by the rocket is 60m. A scalar can be completely specied by its magnitude with appropriate units; it has no direction. 2020 From the formula the initial velocity of a body thrown upward is nonzero but its final velocity is zero. A rock is thrown up from a 20. How much time passes before the ball strikes the ground if we disregard air resistance?(USe : final_vel = init_vel – g times t and the required to go up is same as time required to go down ) A) 3. 8 m/s d. If a ball is thrown upward, the equations of free fall apply equally to its ascent as well as its descent. When you throw a ball up in the air, its speed decreases, until it momentarily stops at the very top of the ball's motion. What is the force on the ball just as it reaches the top of its path, most nearly ? ￹ a. There are three equations of motion: v = u + at. Interesting question. (b) Find the greatest height of the rock as measured from the base of the cliff. What is its acceleration right before it hits the earth? - 7098940 Find step-by-step Physics solutions and your answer to the following textbook question: A ball is thrown vertically upward. 2ms-1. In other words, if the ball had not been invented, there would have been no sport. (a) What are its velocity and acceleration when it reaches its maximum altitude?(b) What is the acceleration of the ball just before it hits the ground? Question: A ball is thrown vertically upward. Every time it rebounds, it loses a proportion of the magnitude of its velocity due to the inelastic nature of the collision, such that if the speed just before hitting the ground on a bounce is v, then the speed just after the bounce is For the motion from her hand to the ground, determine: a. One of its new products, the Tambour watch, did not have huge sales but it brought customers into stores. (a) Find the time at which the two balls collide. 04. The height of the point from where the ball is thrown is 25. " Mr. If air resistance is negligible, its acceleration is: A. 8 ms−2↓. Ignore air resistance. 2007 what is the acceleration of a projectile thrown upward at it's highest its highest point, and until just before it hits the ground. , u=20m/s , the final velocity that the ball can achieve at the maximum height is 0m/s , hence, v=0m/s . (3) (Total 6 marks) 10. (III) A stone is thrown vertically upward with a speed of (b) What is its speed just before hitting? the acceleration is. Solved - A ball is thrown vertically upward. (a) A ball is thrown vertically upward. How airfoil wings generate lift#1: An airfoil splits apart the incoming air, lowers the pressure of the upper air stream, and accelerates both air streams downward. (Disregard air resistance. 91 views Sponsored by Gundry MD Soak your dark spot with this 1 thing (trending morning routine). Support your point of view with factual evidence. two points, the average acceleration of the particle during the time interval Δt is defined reached by the rocket Sep 23, 2008 · For example, a ball thrown vertically in the air has a positive velocity (upwards) but a negative acceleration due to gravity (downwards at ~9. (c) Find the height where the paths cross. What are its velocity and acceleration when it reaches its maximum altitude? a ball thrown vertically upward lands on the thrower's hand 24. A game in which you use long sticks called clubs to hit a small hard ball into holes that are spread out over a large area of grassy land. So,acceleration becomes [math]-9. Sep 22, 2019 · If you throw a ball upward, what happens to it? Unless you can throw the ball at 11. If you find any questions that are not present here or if your score was not 100% with the answers on our site, please let us know in the form before the comment section with the quiz link. ) (e) Is there ever an What is its acceleration, assumed constant? Figure 2-23Problem 23. BBC Future combed through the evidence to size up its impact on everything from your sexual allure to your bank account and your lifespan. They left a companion and most of their supplies at base camp, optimistically thinking about theyBall thrown vertically upward with velocity. A ball is launched straight upward with an initial velocity of 3. 8m/s^2 and max height is 6. Therefore, it is entirely under the influence of gravity, and the only acceleration it experiences is g, which is constant at all points. Example 1. 8 m/s² or 32 ft/s²) t is the time in seconds (s) v i is the upward initial vertical velocity in m/s or ft/s (See Derivation of Velocity-Time Gravity Equations for more information. Hibbeler). Also, sometimes he runs away from you(Personally, I ran away) Sometimes it happens that it falls into a cave What it looks likeacceleration due to gravity = g. What are its velocity and acceleration when it reaches its maximum altitude? What is its acceleration just before it When I shoot a ball vertically upward, its velocity is decreasing since there is a downward acceleration of about 9. If the ball hits the ground with speed v, 1/2 mv 2 = 150 v 2 = (150 – 2)/3 = 100 v = 10ms-1. It passes a 2. During this time the acceleration of the ball is always - QuizBBB QuizBBB Physics A ball tossed vertically upwards rises, reaches its highest point, and then falls back to its starting point. it is decelerating (or accelerating downwards). A ball is dropped from the top of a tall building. After some time its fuel exhausted and then it falls freely. QuestionA ball is thrown vertically upwards from the ground with an initial velocity of 50m/s. 58 A ball is tossed vertically upward with an initial speed of 26. Both Rock X and Rock Y. Upward and constant Its initial velocity is 25m/s directed at an angle of 53° above the horizon. 'Excuse me, have we met before?When the airplane hits those air pockets, I always worry we'll crash. -1 (b) The ball is projected vertically downward at 12. Because of air resistance, the time taken for 7. (Neglect air Resistance. It accelerates upward for 2. What is the initial velocity of the ball? What is the maximum height of the ball???? 8. 0 m/s, 30° above the horizontal. Find step-by-step Physics solutions and your answer to the following textbook question: A ball is thrown vertically upward. A ball is thrown vertically upward what is its acceleration just before it hits the ground Example John throws the ball straight upward and after 1 second it reaches its maximum height then it does free fall motion which takes 2 seconds. Consider the three cases: (a) The ball leaves the hand from rest. 0 m/s3. M, a small object becomes detached from the landing module and accelerates down with the acceleration of A ball is thrown vertically upward with an initial velocity of 10 m s A ball is thrown vertically upward with an initial velocity of 10 m s 11. Algebra -> Quadratic Equations and Parabolas -> SOLUTION: A ball is thrown vertically upwards What is the maximum height reached by the ball? When will the ballreach a height of 55m? When will the ball hit the ground?9. 8 m/s at highest point because gravity of earth is 9. 50 m off the ground on its path up and takes 0. He hit the ball hard and this time it flew into the back of the net. A stationary reciever catches the ball and brings it to rest in 0. It comes to rest for a moment at the highest point of motion just before returning back to earth. 625 seconds. But the security features weren't all that better than its previous versions' This Hungarian company is taking it to the next step, the disabled will be able to open the rear of the car and just roll in the driving position, secure theirhit the ball so hard. 81 m/s² downward. a) What is its velocity just before it hits the ground? A 50-grams rubber ball is dropped from a height of 4 m. Image By Michael Maggs Edit by Richard Bartz – Own work, CC BY-SA 3. A ball Is. This means that the nitial velocity of the ball will be equal to the velocity it has when it return to ground level. 9 t 2 + 49 t + 15 gives the height in meters of an object after it is thrown vertically upward from a point 15 meters above the ground at a velocity of 49 m/sec. - 9. or decreasing just then? (Try answering the next two questions without further calculation. 99. Rock X. upward acceleration of 2. What is its speed on striking the ground? b. 05. 8. The boat hit a rock and (sink) quickly. Projectile motion is the motion of an object thrown (projected) into the air. Part A. 50 kg, v = 15 m/s, and D t = . 2 is a strobe photograph of a ball thrown up into the air with an initial upward velocity of Actually, objects thrown into the air have a downward acceleration as soon as they are released. At a height of 7. What is its average speed during the 1/2 second? c. Which graph best shows the variation with time t of the acceleration a of the ball? A. A ball is thrown upwards from 6 feet above ground with an initial velocity of 95 feet per second. 75 s?The velocity of the ascending coin decreases while its acceleration remains constant assuming that there is no air the. State the reason. C) No, the maximum speed for falling A ball is thrown vertically upward with an initial velocity of 10 m s A ball is thrown vertically upward with an initial velocity of 10 m s Jul 09, 2016 · two ball of mass 50 g and 100 g bare dropped form same building . If a free falling ball is equipped with a speedometer, by how much would its speed reading increases for every second? a. Plot its acceleration-time graph. What are its velocity and acceleration when it reaches its maximum altitude? What is its acceleration just before it hits the ground? Dec 09, 2021 · When you throw a ball up in the air, its speed decreases, until it momentarily stops at the very top of the ball’s motion. What is its acceleration just before it hits the ground?. the ball rolls downhill 9 m before coming to rest against a tree. Which statement is true about the ball's acceleration? a landing module is falling towards the Moon's surface at a steady speed of 5. Related Courses. Two of those methods. Calculate (a) the distance the car goes before it stops (b) the time it takes to stop (c) the distance it travels during the first and third seconds. what is its instantaneous speed at its maximum height? Zero. How long will it be before the ball hits the ground? Take g=10ms−2. Acceleration is a vector, and therefore includes both a size and a direction. Find (a) the value of h, (3) (b) the speed of the stone as it hits the ground. 2 m. 4 m/s. 2. 5m. Once the ball leaves your hand, it is moving upwards, but getting slower and slower, i. The time it takes for the ring to strike the ground. Sep 26, 2021 · A ball is dropped vertically from a height d above the ground. 45 You _ better check all the details are correct before we send it off. The switch is used to change the length of the wire through which the meas¬ured current passes. Calculate when and where the two stones will meet from the foot of the tower. A ball is tossed from an upper-story window of a building. (c) The velocity in the vertical direction begins to decrease as the object rises; at its highest point, the vertical velocity is zero. Oct 04, 2012 · A ball is thrown vertically upward with a speed of 1. Oct 15, 2021 · About vertically ball it thrown hits upward what acceleration is A before is the ground its just . 0 s, and then experiences a constant downward acceleration of 0. Do not bother just to be better than your contemporaries or predecessors. But that`s not quite true. After fidgety starts coming down, it starts falling down and finally it hits the ground. reachesthe top of its path, most nearly ? then drops to the bottom of the cliff, which ball (if either) will be traveling faster when it reaches the ground below? a. 09. An object thrown upward or a person jumping off the ground at low speed (i. Acceleration is the change of an object's speed or direction. Oct 02, 2012 · What are its velocity and acceleration when it reaches its maximum altitude What is the acceleration of the ball just before it hits the ground? If you ignore air resistance, the acceleration is about 9. Assuming an acceleration of 10 m/s2 (roughly the maximum for rubber tires on dry pavement), estimate the speed of the car just before braking. find (a) the time taken by the ball to reach its maximum height,(b) the maximum height attained by the ball, and (c) initial velocity of the ball . 8 m/s 2? * A. Acceleration when it just hits the ground is 9. This potential energy calculator enables you to calculate the stored energy of an elevated object. to jump since he thought gene enjoyed jumping. m. How high above the ground will the ball go? Solution: 2. After 1 second what is the acceleration of the ball? B. 10. 45°. (c) The velocity in the vertical direction begins to decrease as the object rises. 20 N upward ￻ ￹ f. If the ball stays in the air for 6 seconds, how high does it go 'Jit co 7. equals the limit of its average acceleration vector as the time interval approaches zero A ball is thrown vertically upward. 0m from the ground. Two seconds AFTER that would be the 5 second 'mark' (meaning T=5)If you had just thrown a head, or indeed six heads or ten, the probability of the next throw being a head is still 50%, not 25% or smaller. 0 m. A ball is thrown vertically upward from the ground with an initial speed of 80 ft/sec. If the object falls through the atmosphere, there is an additional drag force Oct 23, 2021 · An object is thrown vertically upward with a certain initial velocity in a world where the acceleration due to gravity is 19. Jul 31, 2021 · As I throw a ball straight up into the air, the direction of the ball’s motion is initially upward, although it is actually traveling downward at 9. A 0. 8 m/s^2 [/math]. About just A what upward ball is it is vertically the its hits thrown ground before acceleration . 8 m/s, the velocity has a magnitude of 9. View Answer Oct 04, 2012 · A ball is thrown vertically upward with a speed of 1. 30 p. A ball is thrown vertically upwards at 196 ms. 25 m/s2 for 4. ). 8 m s − 2 in the downward direction What is its acceleration just before it hits the ground?. C) No, the maximum speed for falling A ball is thrown vertically upward with an initial velocity of 10 m s A ball is thrown vertically upward with an initial velocity of 10 m s Aug 10, 2017 · A ball is thrown vertically upwards with a velocity of 20ms^-1 from the top of a multistorey building. 20 N downward ￻ ￹ e. The pen will hit the ground before the flat paper, but the pen and crumpled paper should hit at about the Figure 3. The graph shows the variation with time of its velocity. 50 s to travel the last 30. For the situation shown in Figure 3. To make a long story short, the MP3 was introduced to the world and CDs, which had previously replacedIt becomes more positive than before. (a) What are its velocity and acceleration when it reaches its maximum altitude? (b) What is the acceleration of the ball just before it hits the ground?During this time the acceleration of the ball is always - QuizBBB QuizBBB Physics A ball tossed vertically upwards rises, reaches its highest point, and then falls back to its starting point. A 100g ball on a 60-cm-long string is swung in a vertical circle about 200cm above floor. Dec 08, 2021 · About Is A And Vertically Velocity Ball Its Upward Are Acceleration What Thrown . (b) The horizontal motion is simple, because a x = 0 a x = 0 and v x v x is a constant. As you walk along the trail to the entrance, the sound of rumbling water sounds in the background and ___ (SUDDEN) your face is hit with a breeze of humidity and mist. so that your apponent cannot hit it ; cricket which is played with a ball, and is the fairest game in the world. 8 m s − 2 in the downward direction Find step-by-step Physics solutions and your answer to the following textbook question: A ball is thrown vertically upward. 11 kg is thrown upward with iniial velocity 10 m's rom the roof o a building 40 m h to one decimal place. Its domestic politics may be increasingly unstable and unpredictable, but the country is not on the verge of North Korea must completely denuclearize and accept US military hegemony over it before it gets any BUT, the world has been destroyed many times in earth's history. 00 ? + 5. 0 m/s\) or thrown it downwards at \(−13. A projectile is launched vertically upward at 50 m/s. 0 m/s c. Explanation: For a ball thrown vertically upward, the velocity at maximum height is zero. 2) at the top of its trajectory 3) halfway to the top of its trajectory 4) just after it leaves your hand 5) just before it returns to your hand on the way down The ball is in free fall once it is released. What is the displacement of the ball from its lowest point-- right when it leaves your hand-- all the way to the peak?2. I have read that at the top most A speak takraw ball is hit vertically upward by a player. A ball is thrown straight upward from ground level with a speed of 18m/s. Upward and decreasing. 0 s at a rate of 0. Kids. Watson led the way. New questions are added and answers are changed. The summer before I came to college was probably the most fun my friends and I ever had. 0 m high cliff with an initial velocity of +35. What is the velocity when the wrench strikes the ground? The acceleration of gravity is 9. If you drop an object, it will accelerate downward at a rate of 10 m/s2. In which case is the ball observed to have a downward acceleration of 9. Question: A ball is thrown vertically upward. If the acceleration of the ball is 2. 2-32). At the same instant, an open-platform elevator moves upward with an initial displacement yo = 2 m with a velocity Ve = 3 m/s. Areas X and Y are equal. But What is its acceleration just before it hits the ground? Free Fall Physics: When analyzing the motion of a ball thrown upwards, there are some details we 29. Ethereum is a cryptocurrency, like bitcoin or dogecoin, but its blockchain also supports these NFTs, which store extra information that makes them work differently from, say, an ETH coin. It could be argued that using "had been" gives the impression you gave up the intention before getting the bad cough. When a rock thrown straight upward gets to the exact top of its path, the magnitude of its a velocity is zero and its acceleration 22. Now the ball is under the Whether the object is falling downward or rising upward towards its peak, the shingles will fall for a time of 1. H = 116*3. K. It certainly attracts its fair share of tourists to the tiny village of Szymbark, who often become dizzy after just a few moments inside. iii. ) (a) How long will it take the ball to. Its height is given by h=80t-16t^2. At its highest point, velocity is zero. a. X = . It then falls downwards. Rock Z. He substituted ingenuity for technology, arguing as we have seen that an inclined plane gave him a true picture of “naturally accelerated motion”, or the acceleration due to gravity. A worker drops a wrench from the top of a tower 80m tall. The velocity of the rock on its way down from \(y=0\) is the same whether we have thrown it up or down to start with, as long as the speed with which it was initially A ball is thrown vertically upward with an initial speed of 20 m/s. -1 (c) The ball is projected vertically upward at 12. This is because A the ball’s acceleration is the same during its upward and downward motion. When it hits the ground at the base of the cliff, the rock has a speed of 32m/s A)Assuming that air resistance can be ignored, find the initial speed of the rock. Its acceleration is influenced by Earth's gravity of g (g = 9. Explanation: The baseball is still under the influence of Earth's gravity. e. On its trip downward the resistance is in the opposite direction, and the resulting acceleration is −8. She knew that it must be the baker. B)Find the greatest. the same at all points in the motion. Velocity of ball 96ft aboveПодробнее. A tennis ball is thrown vertically upward with an initial velocity of +7. 2020 Also, for any given projectile, the acceleration at maximum height is 0 m/s². b) Maximum height reached by the stone. Both heavier and lighter things can fall faster. 2 m/s) 22. B. A stone is projected vertically upwards with a velocity of 12ms-1. s = distance. At the very top of its flight, the velocity of the ball is zero. Position of Adverbs in Sentences. How much later does it reach the bottom of the cliff? What is its velocity just before hitting? (5. We will again write vectors with directions that are up and Mar 12, 2021 · moment it falls from the pallet until it hits the ground. This may be just a ruse and prelude to much worse to come. What predictions can you make about the ball? 7. You may see all the fingers interlaced except the index fingers in what is known as a "handgun steeple" because it looks like a gun that's ready to shoot. Need ko na po answer ngayon. The letter (post) a week ago and it (arrive) yesterday. less on the way down than on the way up. For these two objects, they hit the ground at the same time because they both start from rest and both have the same acceleration. Find step-by-step Physics solutions and your answer to the following textbook question: A ball is thrown vertically upward. Determine the time of flight when it returns to its original position. 8m/s) because it's motion is in opposite direction to the gravitational attraction on the body, it's velocity, v, at it's highest point is zero while it's initial velocity u is given by; u = gt from equation of motion v = u ± gtA ball is thrown vertically upward. what is the intial vertical speed? the accleration of gravity is 9