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1 HW - FREE FALL REG 1. Starting from rest, a particle confined to move along a straight line is accelerated at a rate of 2 5.0 m/s . Which one of the following statements accurately describes the motion of this particle? a. The particle travels 5.0 m during each second. b. The particle travels 5.0 m only during the first second. c. The speed of the particle increases by 5.0 m/s during each second. 2 d. The acceleration of the particle increases by 5.0 m/s during each second. e. The final speed of the particle will be proportional to the distance that the particle covers. 2. The baseball catcher throws a ball vertically upward and catches it in the same spot as it returns to the mitt. At what point in the ball’s path does it experience zero velocity and nonzero acceleration at the same time? a. midway on the way up b. at the top of its trajectory c. the instant it leaves the catcher’s hand d. the instant before it arrives in the catcher’s mitt 3. Ball A is dropped from rest from a window. At the same instant, ball B is thrown downward; and ball C is thrown upward from the same window. Which statement concerning the balls is necessarily true if air resistance is neglected? a. At some instant after it is thrown, the acceleration of ball C is zero. b. All three balls strike the ground at the same time. c. All three balls have the same velocity at any instant. d. All three balls have the same acceleration at any instant. e. All three balls reach the ground with the same velocity. 4. A rock is thrown vertically upward from the surface of the earth. The rock rises to some maximum height and falls back toward the surface of the earth. Which one of the following statements concerning this situation is true if air resistance is neglected? a. As the ball rises, its acceleration vector points upward. b. The ball is a freely falling body for the duration of its flight. c. The acceleration of the ball is zero when the ball is at its highest point. d. The speed of the ball is negative while the ball falls back toward the earth. e. The velocity and acceleration of the ball always point in the same direction. 5. A ball is in free fall. Its acceleration is: a. downward during both ascent and descent b. downward during ascent and upward during descent c. upward during ascent and downward during descent d. upward during both ascent and descent e. downward at all times except at the very top, when it is zero 6. A ball is in free fall. Upward is taken to be the positive direction. The displacement of the ball is: a. positive during both ascent and descent b. negative during both ascent and descent c. negative during ascent and positive during descent d. positive during ascent and negative during descent e. none of the above 7. A baseball is thrown vertically into the air. The acceleration of the ball at its highest point is: 2 a. 9.8 m/s down 2 b. 9.8 m/s up 2 2 c. changing suddenly from 9.8 m/s up to 9.8 m/s down d. zero e. cannot be calculated without knowing the initial velocity 8. Which one of the following statements is correct for an object released from rest? a. The average velocity during the first second of time is 4.9 m/s b. During each second the object falls 9.8 m c. The acceleration changes by 9.8 m/s every second d. The object falls 9.8 m during the first second of time e. The acceleration of the object is proportional to its weight 2 9. A freely falling body has a constant acceleration of 9.8 m/s2. This means that: a. the body falls 9.8 m during each second b. the body falls 9.8 m during the first second c. the speed of the body increases by 9.8 m/s during each second 2 d. the acceleration of the body increases by 9.8 m/s during each second 2 e. the acceleration of the body decreases by 9.8 m/s during each second 10. An object is shot vertically upward. While it is rising: a. its velocity and acceleration are both upward b. its velocity is upward and its acceleration is downward c. its velocity and acceleration are both downward d. its velocity is downward and its acceleration is upward e. its velocity and acceleration are both decreasing 11. The coordinate-time graph of an object is a straight line with a positive slope. The object has: a. constant displacement b. steadily increasing acceleration c. steadily decreasing acceleration d. constant velocity e. steadily increasing velocity 12. Which of the following five coordinate versus time graphs represents the motion of an object whose speed is increasing? a. I b. II c. III d. IV e. V 13. The diagram shows a velocity-time graph for a car moving in a straight line. At point Q the car must be: a. moving with zero acceleration b. traveling downhill c. traveling below ground-level d. reducing speed e. traveling in the reverse direction to that at point P 14. Which would fall with greater acceleration in a vacuum, a leaf or a stone? a. the leaf b. the stone c. They would accelerate at the same rate. d. It is difficult to determine without more information. 15. A ball is thrown upwards with a speed of 24 m/s. (a) When is the velocity of the ball 12.0 m/s ? (b) When is the velocity of the ball - 12.0 m/s? (c) What is the displacement of the ball at those times? (d) What is the velocity of the ball 1.50 s after launch? (e) What is the maximum height reached by the ball? 2 Take the acceleration due to gravity to be 10 m/s . 3 16. King Kong carries Fay Wray up the 321-m-tall Empire State Building. At the top of the skyscraper, Fay Wray’s shoe falls from her foot. How fast will the shoe be moving when it hits the ground? 17. The Steamboat Geyser in Yellowstone National Park, Wyoming is capable of shooting its hot water up from the ground with a speed of 48.0 mIs. How high can this geyser shoot? 18. A baby blue jay sits in a tall tree awaiting the arrival of its dinner. As the mother lands on the nest, she drops a worm toward the hungry chick’s mouth, but the worm misses and falls from the nest to the ground in 1.50 s. How high up is the nest? 19. A unique type of basketball is played on the planet Zarth. During the game, a player flies above the basket and drops the ball in from a height of 10 m. If the ball takes 5.0 s to fall, find the acceleration due to gravity on Zarth. 20. During an Apollo moon landing, reflecting panels were placed on the moon. This allowed earth-based astronomers to shoot laser beams at the moon’s surface to determine its distance. The reflected laser beam was observed 2.52 s after the laser pulse was sent. If 8 the speed of light is 3.00 X 10 m/s, what was the distance between the astronomers and the moon? 4 21. If an object were equipped with a speedometer and allowed to fall freely on a planet where the acceleration due to gravity is 20 m/s2, the reading on the speedometer increases each second by a. 10 m/s. d. 40 m/s. b. 20 m/s. e. a rate that depends on its initial speed. c. 30 m/s. 22. Ten seconds after starting from rest, a freely falling object will have a speed of about a. 10 m/s. c. 100 m/s. e. more than 500 m/s. b. 50 m/s. d. 500 m/s 23. If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting point is about a. 1 second. d. 20 seconds. b. 2 seconds. e. not enough information to estimate c. 10 seconds. 24. The vertical height attained by a basketball player who achieves a hang time of a full 1 second is about 25. If a projectile fired beneath the water, straight up, breaks through the surface at a speed of 16 m/s, to what height above the water will it ascend? 26. A stone is dropped from a cliff. After it has fallen 40 m, what is the stone's velocity? 27. During one second time interval, the object changed the speed from 10 m/s to 20 m/s. What is the average speed of the object during this 1s interval? What is its acceleration? What type of the motion are we probably talking about? 5 28. An apple drops from a tree and hits the ground in one second. What is its speed upon striking the ground? What is its average speed during the one second? How high above the ground was the apple when it first dropped? 29. Calculate the acceleration of a car (in km/h.s) that can go from rest to 100 km/h in 10 s. 30. An object is dropped from rest and falls freely. After 6 seconds, calculate its instantaneous speed, average speed, and distance fallen. 6 HW - FREE FALL REG 1. C 2.B 3.D 4.B 5.A 6.D 7.A 8.A 9.C 10.B 11.D 12. A 13.E 14.C 15.(a) 1.2 s (b) 3.6 s (c) 21.6 m (d) 9.0 m (e) 28.8 m 2 2 2 16. vi = 0 m/s g = 10.0 m/s vf = vi + 2 gd + d = 321 m 2 1/2 2 1/2 2 2 1/2 vf = (vi + 2 gd) = (2(10.0 m/s )(321 m)) = (6420 m /s ) = 80.1 m/s 17. vi = 48.0 m/s + vf = 0 m/s 2 2 2 g= 10.0m/s vf = vi + 2 gy 2 2 y =( vf - vi )/2g = —115 m 2 18. vi = 0 m/s g = 10.0 m/s 2 t = 1.50 s y = vit + ½ g t y = 11.3 m 2 19. g = 0.8 m/s 8 8 20. d = v t = (3.00 X 10 m/s)(1.26 s) = 3.78 X 10 m 21. B 22.C 23.B 24. 1.2 m. 25.12.8 m 26.28 m/s 27. assuming constant acceleration. vavg = 15 m/s 2 acceleration is: a = 10 m/s v = gt 2 28. speed = (10 m/s )(1s) = 10 m/s average speed assuming constant acceleration. vavg = 5 m/s distance: d = vavg t = (5 m/s)(1s) = 5 m or d = ½ g ( t ) = 5 m 2 29. a = v/t = (100 km/h)/10s = 10 km/h/s = 2.8 m/s2 30. vf = vi +a t = 0 + 10 m/s2 x 6 s =60 m/s; assuming constant acceleration = (0m/s + 60m/s)/2 vavg = 30 m/s; d = vavg t = 30 m/s x 6s = 180 m d = ½ g (t ) = 180 m 2 or

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posted: | 11/8/2011 |

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