Projectile Motion Name____________________________

Practice and Review

Conceptual

1. You drop your ski pole while riding in a moving chair lift. From your position on the chair lift, what path do you observe the ski pole to take? Ignore air resistance.

2. Give two examples of scalars and two examples of vectors.

3. The horizontal acceleration of a projectile is ____ as its position changes.

a. zero b. decreases c. is constant d. increases

3. The initial horizontal velocity of a projectile is ____ its final horizontal velocity.

a. greater than b. less than c. equal to

4. For a fast ball to pass the height of a batter’s chest, the pitcher must aim the ball ____.

a. exactly at the height of the batter’s chest

b. slightly below the height of the batter’s chest

c. just above the height of the batter’s chest

5. Two cannonballs, A and B, are fired from the ground with identical speeds, but with qA larger than qB. (a) Which cannonball reaches a higher elevation? (b) Which stays in the air longer? (c) Which has the greater range?

6. A projectile is launched at an angle of 30° to the horizontal with a speed of 30 m/s. How does the horizontal component of its velocity 1.0 s after launch compare with its horizontal component of velocity 2.0 s after launch?

7. At what point in its path does a projectile have minimum speed? Explain.

8. Is it possible for a projectile’s velocity to be at right angles to its acceleration? If so, give an example.

9. Child 1 throws a snowball horizontally from a rooftop. Child 2 throws a snowball straight down from the same location. Once in flight, is the acceleration of snowball 2 greater than, equal to, or less than the acceleration of snowball 1? Explain

10. A ball is dropped off the edge of a desk and falls vertically. Another ball rolls off the desk with some horizontal speed at exactly the same time. Circle the letter that best describes the vertical component of the velocity of the balls as they strike the ground.

a. Equal b. Opposite c. Zero d. Constant

11. Considering the two balls as described in #10, which ball hits the ground with the greatest overall speed? Explain.

Vectors

12. Find the x and y components of a 34 m displacement that is 22 degrees west of south.

13. Find the resultant velocity of 3.0 m/s east and 7.0 m/s south.

14. To remove a tree from the ground, Jackie pulls with a force of 240 N at 35° North of East and Sean pulls with a force of 310 N at 25° North of East. What is the resultant force felt by the tree?

15. A remote control airplane is set to fly with a velocity ff 15 m/s in a direction 30.0° North of West. If a wind is blowing the airplane at 8 m/s in a direction of 10.0° East of South, what is the resultant velocity of the airplane?

Projectile Problem Solving

16. Tom the cat is chasing Jerry the mouse across a table surface 1.5 m above the floor. Jerry steps out of the way at the last second, and Tom slides off the edge of the table at a speed of 5.0 m/s. Where will Tom strike the floor?

17. The fastest recorded pitch in Major League Baseball was thrown by Nolan Ryan in 1974. If this pitch were thrown horizontally, the ball would fall 0.809 m by the time it reached home plate, 18.3 m away. How fast was Ryan’s pitch?

18. Measurements made in 1910 indication that the common flea is an impressive jumper, given its size. Assume that a flea’s initial speed is 2.2 m/s, and that it leaps at an angle of 21 degrees with respect to the horizontal. If the jump lasts 0.16 s, what is the magnitude of the flea’s horizontal displacement? How high does the flea jump?

19. A ball is thrown from a roof with a speed of 10.0 m/s and an angle of 37 degrees with respect to the horizontal. What are the vertical and horizontal components of the ball’s displacement 2.5 seconds after it is thrown?

20. A beach ball, moving with a speed of 1.25 m/s, rolls off a pier and hits the water 0.71 m from the end of the pier. How high above the water is the pier?

21. A person standing at the edge of a seaside cliff kicks a stone over the edge with a speed of 18 m/s. This cliff is 52 m above the water’s surface.

a. How long does it take for the stone to fall to the water?

b. With what speed does it strike the water? (Note: If I would have asked for velocity then you would have had to include a direction!)

22. A downed pilot fires a flare from a flare gun. The flare has an initial speed of 250 m/s and is fired at an angle of 35 degrees to the ground. How long does it take for the flare to reach its maximum altitude?

23. An arrow is shot at 30.0° above the horizontal. Its velocity is 49 m/s and it hits the target.

a. What is the maximum height the arrow will attain?

b. The target is at the height from which the arrow was shot. How far away is it?

24. A discus is released at an angle of 34° to the horizontal and with a speed of 22.0 m/s.

a. How long does it stay in the air?

b. What horizontal distance does it travel?

25. A coin rolls along the top of a 1.33 m height desk with a constant velocity. It reaches the edge of the desk and hits the ground 0.25 m from the edge of the desk. What was the velocity of the coin as it rolled across the desk?