Name: __________________ Due Date: ________

Miss Shea Physics 9 One Leader Changes Everything

Unit 3: Projectile MotionHomework Packet

Directions: Each day I will inform you of what questions you should be able to complete. The next day in class

you may have a quiz, a do-now, or the opportunity to ask questions in class based on the homework from the night

before. It is in your best interest to complete the homework every night. The packet will be collected and

graded on the day of the unit exam.

1

Topic 1: Free Fall

1. Draw the position versus time graph for an object dropped from a height of 25 m. How far will an object in free-fall near earth’s surface fall in 3.0 seconds?

2. An object starts from rest and falls freely near Earth’s surface for 3.00 seconds. Determine the final speed of the object.

3. A baseball is dropped off a cliff and it accelerates to the ground at a rate of -9.8 m/s2. If the cliff is 120 m high, how long before the ball hits the ground?

4. A coin is dropped in a vacuum tube, find its displacement after .30 seconds.

2

5. An object dropped on planet X falls 64 m in 4 seconds. Find the acceleration due to gravity on planet X.

6. (a) How long does it take a ball to fall from a roof to the ground 7.0 m below? (b) With what speed does it strike the ground?

7. A peso is dropped into a well and it falls for 3 seconds before hitting the water. What is the peso's average speed during its 3 second drop?

8. A rock is dropped from the top of an overhang and strikes the ground 6.5 seconds later. How high is the overhang in meters?

3

9. It takes 0.210s for a dropped wrench to travel past a poster that is 1.35 meters tall. How high above the top of the poster was the wrench released?

Topic 2: Vertical Projectiles

10. What is the acceleration of a projectile on earth when it reaches its maximum height?

11. Which statement is true concerning the ball when it is at C, the highest point in the trajectory?

a. The ball’s velocity and acceleration are both zero.b. The ball’s velocity is perpendicular to its acceleration.c. The ball’s velocity is not zero, but its acceleration is zero.d. The ball’s velocity is zero, but its acceleration is not zero.

12. 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 of of the following statements concerning this situation is (are) true if air resistance is neglected?

e. As the ball rises, its acceleration vector points upward.f. The ball is freely falling during the duration of its flight.g. The acceleration of the ball is zero when the ball is at its highest

point.h. The speed of the ball is negative while the ball falls back toward

the earth.i. The velocity and acceleration of the ball always point in the

same direction.

13. A ball is thrown vertically upward from the surface of the earth. Consider the following quantities: (1) the speed of the ball; (2) the velocity of the ball; (3) the acceleration of the ball.

4

Which of these is (are) zero when the ball has reached the maximum height?

a. 1 onlyb. 2 onlyc. 1 and 2d. 1 and 3e. 1, 2, and 3

14. A rocket is fired vertically upward with an initial velocity of 29 m/s. Find the rocket's maximum altitude.

15. When you drop a ball it accelerates downward at 9.8 m/s2. If you instead throw it downward, then its acceleration immediately after leaving your hand, assuming no air resistance, is

a) 9.8 m/s2. b) more than 9.8 m/s2. c) less than 9.8 m/s2.d) Cannot say, unless the speed of throw is given.

16. A stone is thrown vertically upward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high. How long does it take to reach the bottom of the cliff?

17. You throw a ball downward from a window at a speed of 2.0 m/s. The ball accelerates at 9.8 m/s2. (a) How fast is it moving when it hits the sidewalk 2.5 m below? (b) If you throw the same ball up instead of down, how fast is it moving when it hits the sidewalk?

5

18. A ball is thrown straight up with a speed of 4.6 m/s. How long does the ball take to reach its maximum height?

19. A round is launched straight up at 460 m/s. How long will it take it to reach its apex and how high will that be? (air resistance may be neglected.)

Topic 3: Horizontal Projectiles (cliff problems)

20. A ball is projected horizontally from the top of a 92.0 meter high cliff with an initial speed of 19.8 m/s. Determine (a) the horizontal displacement, (b) the final speed the instant prior to hitting the ground.

6

21. Determine the launch speed of a horizontally launched projectile that lands 26.3 meters from the base of a 19.3 meter high cliff.

22. A soccer ball is kicked horizontally at 15.8 m/s off the top of a filed house and lands 33.9 meters from the base of the field house. Determine the height of the field house.

23. A bullet is aimed at a target on the wall a distance L away from the firing position. Because of gravity, the bullet strikes the wall a distance y below the mark as suggested in the figure below. Note: The drawing is not to scale.

If the distance L were half as large, and the pullet had the same initial velocity, how would y be affected?

a. It would double.b. It would be half as large.c. it would be four times larger.d. it would be one fourth as large.

7

e. it is not possible to determine unless numerical values are given for the distances.

24. A spring loaded gun is aimed horizontal and is used to launch identical balls with different initial speeds. The gun is at a fixed position above the floor. The balls are fires one at a time. If the speed of the second projectile fired is twice the speed of the first projectile fires, how is the horizontal range affected?

25. A baseball is launched horizontally from the top of a cliff with an initial velocity of 20 m/s. The trajectory of the ball is shown below. Express your understanding of motion by filling in the blanks.

26. If the ball in the diagram above strikes the ground after four seconds, then how high was the cliff? How far from the base of the cliff did the ball land?

8

27. I throw a ball off the edge of a 15.0m tall cliff. I threw it horizontally at 8.0m/s.

a. Determine how much time it takes to fall.b. Determine how far from the base of the cliff it hits the ground.c. Determine how fast it is moving vertically when it hits the

ground.d. Determine what its total velocity is when it hits the ground.

28. A pool ball leaves a 0.60-meter high table with an initial horizontal velocity of 2.4 m/s. Predict the time required for the pool ball to fall to the ground and the horizontal distance between the table's edge and the ball's landing location.

29. A soccer ball is kicked horizontally off a 22.0-meter high hill and lands a distance of 35.0 meters from the edge of the hill. Determine the initial horizontal velocity of the soccer ball.

Topic 4: Projectiles (launched at an angle)

30. A football is kicked at an angle of with respect to the horizontal. Which one of the following statements best describes the acceleration of the football during this event if air resistance is neglected?

e. The acceleration is zero meters per second per second at all times.

f. The acceleration is 9.8 meters per second per second at all times.

g. The acceleration is zero when the football has reached the highest point in its trajectory.

h. the acceleration is positive when the football rises, and its negative as the football falls.

9

i. The acceleration starts at 9.8 m/s2 and drops to some lower constant value as the ball approaches the ground.

31. A baseball is hit upwards and travels along a parabolic arc before it strikes the ground. Which one of the following statements is true?

j. The acceleration of the ball decreases as the ball moves upward.k. The velocity of the ball is zero when the ball is at the highest

point in the arc.l. The acceleration of the ball is zero when the ball is at the

highest point in the arc.m. The velocity of the ball is maximum when it is at the highest

point in the arc.

32. A ball is projected at an angle with an initial horizontal velocity of 8.0 m/s and an initial vertical velocity of 29.4 m/s. The trajectory diagram shows the position of the ball after each consecutive second. Express your understanding of projectiles by fill in the blanks.

10

Use the following information and diagram for the following two questions. A tennis ball is thrown upward at an angle from point A. It follows are parabolic trajectory and hits the ground at point D. At the instant shown the ball is a point B. Point C represents the highest position of the ball above the ground.

33. How do the x and y components of the velocity vector of the ball compare at points B and C?

34. How do the x and y component of the velocity vector of the ball compare at points A and D?

35. A projectile is launched with a speed of 31.1 m/s at an angle of 71.2 above the horizontal. The horizontal and vertical components of the initial velocity are shown in the first row of the data table below.

11

Fill in the table indicating the value of the horizontal and vertical components of velocity and acceleration during the course of the projectile’s motion.

36. Using the information above, determine (a) the displacement of the ball, (b) the height above the ground at its peak, and (c) the final speed of the ball upon hitting the ground.

37. Suppose that the horizontal component of the initial velocity had been 13.0 m/s and the vertical velocity had been unchanged (in the two leading questions). Determine the (a) time of flight; (b) displacement of the ball; (c) height above the ground at the peak; (d) the speed upon hitting the ground.

12

38. Mr Tripp is driving a pick-up truck down Lake Ave. The pick-up is equipped with a projectile launcher that imparts a vertical velocity to a water-filled rubber projectile. While traveling at 20 m/s in an eastward direction, the projectile is launched vertically with a velocity of 58.8 m/s. Fill in the table below that tracks the horizontal and vertical displacement of the projectile every second for the first 12 seconds of the flight.

Time (s) dx (m) dy (m)0.01.02.03.04.05.06.07.08.09.010.011.012.0

39. On the diagram below, place a large dot on the location of the projectile during each second of its trajectory. Draw a smooth curve through the dots to indicate the path traveled.

13

40. Will the projectile land in the truck, behind the truck, or in front of the truck? Assume not air resistance. Explain why you chose your answer.

41. A zoo keeper has a monkey that he must feed daily. The monkey spends most of the day in tress just hanging from a branch. When the zookeeper launches a banana to the money, the monkey has the peculiar habit of dropping from the trees the moment that the banana is launched. Then banana is launched with a speed fo 16.0 m/s a the direction of 51.3 above the horizontal (which is aiming the banana directly at the monkey hanging in the tree). The monkey is initially at rest in the three 25.0 m above the ground. Use kinematic questions to determine the horizontal and vertical displacements of the banana and the monkey at 0.5 second time intervals and fill in the data tables below. Then plot the trajectories of both banana and monkey on the diagram below that.

MonkeyTime (s) dy (m) Height

(m)0.00.51.01.52.0

14

BananaTime (s)

dx (m) dy (m) Height (m)

0.0 0 0 00.51.01.52.0

42. Using trigonometric functions to resolve the following velocity vectors into horizontal and vertical components. Then utilize kinematic equations to calculate the other motion parameters. Be careful with equations and be guided by the principal that “perpendicular components of motion are independent of each other”.

43. Determine the range of a ball launched with a speed of 40.0 m/s at angles of (a) 40.0, (b) 45.0; (c) 50.0.

44. A football is kicked with an initial velocity of 25 m/s at an angle of 45-degrees with the horizontal. Determine the time of flight, the horizontal distance, and the peak height of the football.

15

45. A long jumper leaves the ground with an initial velocity of 12 m/s at an angle of 28-degrees above the horizontal. Determine the time of flight, the horizontal distance, and the peak height of the long-jumper.

46. *A projectile is launched with a speed of 50.0 m/s and an angle of 40.0o above the horizontal, from the top of a 75.0 m high cliff onto a flat valley floor at the base of the cliff. How long does it take for the projectile to reach the valley floor?

47. If I throw a rock off a cliff that is 10 meters high, at a velocity of 10 meters per second at an angle 45 degrees above the horizontal, how far will the rock go before it hits the ground? (Neglect air resistance)

16

Topic 5: Frames of reference

48. A passenger at rest on a flatbed train car fires a bullet straight up. The event is viewed by observes at rest on the station platform as the train moves past the platform with a constant velocity. What is the trajectory of the bullet as described by the observers on the platform?

a. A straight horizontal path in the direction of the train’s velocity.b. A straight vertical path up and down.c. A circular path centered on the gun.d. A straight diagonal path upward.e. A parabolic path.

49. A bicyclist is riding at a constant speed along a straight-line path. The rider throws a ball straight up to a high a few meters above her head. Ignoring air resistance, where will the ball land?

f. Behind herg. In front of herh. In the same hand that threw the balli. In the opposite hand to the one that threw it.j. It cannot be determined without knowing the speed of the rider

and the maximum height of the ball.

50. Consider a transparent elevator accelerating upward with acceleration equal to that of the gravity. If a rock was dropped inside the elevator, what would an observer on the ground see the rock do?

17