9/12 Practice Problems on Freely Falling Objects

1. A ball is dropped from a window 10 m above the sidewalk. Determine the time it takes for the ball to fall to the sidewalk.

2. A camera is accidentally dropped from the edge of a cliff and 6.0 s later hits the bottom. a) How fast was it going just before it hit? b) How high is the cliff?

3. A tennis ball is thrown straight up with an initial speed of 22.5 m/s. It is caught at the same distance above ground. a) How high does the ball rise? b) How long does it take the ball to reach its highest point? c) How long does the ball remain in the air? d) How fast was it going just before it is caught? e) What is the velocity and acceleration of the ball at the highest point?

4. A rock is thrown vertically upward with a velocity of 20 m/s from the edge of a bridge 42 m above a river. a) What is the rock’s speed just before it falls into the river? b) How much time does it take from the time the rock is launched to the time when the rock strikes the river water?

5. A rock is thrown downward from the top of a cliff with an initial speed of 12 m/s. If the rock hits the ground after 2.0 s, what is the height of the cliff? (Disregard air resistance. a = g = 9.81 m/s.)

6. A rock is thrown straight upward with an initial velocity of 24.5 m/s where the acceleration due to gravity has a magnitude of 9.81 m/s. What is the rock’s displacement after 1.00 s?

7.A coin released at rest from the top of a tower hits the ground after falling 1.5 s. What is the speed of the coin as it hits the ground? (Disregard air resistance. a = g = 9.81 m/s.)

8.A rock is thrown straight upward with an initial velocity of 9.6 m/s in a location where the acceleration due to gravity has a magnitude of 9.81 m/s. To what height does it rise?

9.Someone throws a rubber ball vertically upward from the roof of a building 8.00 m in height. The ball rises, then falls. It just misses the edge of the roof, and strikes the ground. If the ball is in the air for 3.00 s, what was its initial velocity? (Disregard air resistance. a = g = 9.81 m/s.)

10. A pair of glasses are dropped from the top of a 32.0 m high stadium. A pen is dropped from the same position 2.00 s later. How high above the ground is the pen when the glasses hit the ground? (Disregard air resistance. a = g = 9.81 m/s.)

11. A pebble falls from the bottom of the basket of a hot-air balloon that is rising at 1.0 m/s. After 3.0 seconds, how far below the basket is the pebble? (Assume no air resistance and a = g = 9.81 m/s.)

Answer:

  1. 1.4 s
  2. A) -59 m/s B) 1.8x102 m
  3. A) 25.8 m B) 2.30 s C) 4.6 s D) 22.5 m/s E) 0 m/s; -9.8 m/s2
  4. A) 35 m/s B) 5.6 s

5.

height of cliff = 44 m

6.

7.

speed = 15 m/s

8.

9.

10.

h = 32.0 m – 1.5 m = 30.5 m

11.