; The total energy does not change in closed systems
; The total momentum does not change in closed systems
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Time for Practice
- You throw a lump of clay with a speed of at a bowling ball hanging from a vertical rope. The bowling ball swings up to a height of compared to its initial height. Was this an elastic collision? Justify your answer.
- The bullet shown above is traveling to the right with a speed of . A block is hanging from the ceiling from a rope in length.
- What is the maximum height that the bullet-block system will reach, if the bullet embeds itself in the block?
- What is the maximum angle the rope makes with the vertical after the collision?
- A new fun foam target on wheels for archery students has been invented. The arrow of mass, , and speed, , goes through the target and emerges at the other end with reduced speed, . The mass of the target is . Ignore friction and air resistance.
- What is the final speed of the target?
- What is the kinetic energy of the arrow after it leaves the target?
- What is the final kinetic energy of the target?
- What percent of the initial energy of the arrow was lost in the shooting?
Answers to Selected Problems
- a. b. 5.
- a. b. c. d. %