1. A 20 kg rock is on the edge of a 100 m cliff. The rock falls from the cliff.
ID: 1991599 • Letter: 1
Question
1. A 20 kg rock is on the edge of a 100 m cliff. The rock falls from the cliff. What speed does the rock have as it strikes the ground?
2. Tarzan swings down from a tree limb that is 4.0 m above the ground. How fast is he going when he reaches the ground?
3. Legend has it that Isaac Newton “discovered” gravity when a 0.20 kg apple fell 7.0 m from a tree. How fast was it going when it hit Newton’s head?
4. A 28 kg boy slides down a ramp from a height of 4.8 m. How fast is the child going at the bottom of the slide?
5. An archer puts a 0.30 kg arrow to his bow. The bow has a spring constant of 155 N/m. The archer draws the bowstring back 0.70 m. If aimed straight up, how high does the arrow go?
6. A roller coaster car starts from rest at the top of a 20 m hill. How fast is the car going when it reaches the bottom?
7. If Abigail can throw a 100 g baseball at 36 m/s, how high would it go?
8. A BB gun can launch a BB with a speed of 52 m/s. If you aim straight up into the air, how high will the BB go?
9. A weightlifter raises a barbell to a height of 1.95 m. She then drops it and it falls to the ground. How fast will the barbell be going?
10. A 50 kg artillery shell is shot from cannon to a maximum height of 400 m. What was the launch velocity?
11. Neil Armstrong can jump straight up with a speed of 1.51 m/s. On the moon, where g = 1.63 m/s2, how high can he jump?
12. Lance Armstrong approaches a hill with a speed of 8.5 m/s. He stops pedaling at coasts up the hill. At what height will he come to a stop?
13. Peekaboo Street starts from rest at the top of a 45 m hill. How fast is she going at the bottom?
14. A toy gun launches a dart with a 1650 N/m spring compressed 0.09 m. If you aim this toy straight up, how high will the 0.0050 kg dart go?
15. A roller coaster car starts from rest at the top of a 20 m hill. (a) How fast is the car going when it reaches the bottom? (b) How fast will the car be going when it gets to the top of the next hill which is 10 m high?
16. A spring-loaded pistol has a 1650 N/m spring. A 22 g pellet is loaded and the spring is compressed 9.0 cm. (a) What is the pellet’s exit velocity? (b) If aimed straight up, how high will the pellet go?
Explanation / Answer
A 20 kg rock, m, is on the edge of a 100 m cliff, h, as shown in Figure 11-20. Assume that air resistance is negligible. (c) What speed does the rock have as it strikes the ground? m/s A 2.4 kg rock initially at rest loses 396 J of potential energy while falling to the ground. Assume that air resistance is negligible. Calculate the kinetic energy that the rock gains while falling. J What is the rock's speed just before it strikes the ground? m/s A railroad car with a mass of 4.9 105 kg collides with a stationary railroad car of equal mass. After the collision, the two cars lock together and move off at 3.7 m/s, as shown in Figure 11-21.
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