關於Conserving momentum的簡單物理問題

Tieria

2009-05-11 12:49 am

1. For each of the following cases, state the type of collision (elastic or inelastic) and give reasons.
(a) A bullet penetrates an apple, which becomes warmer than before.

Ans.: inelastic collision

2. An air-rifle bullet of mass 6g is fired into a lump of plasticine on the back of a trolley of mass 0.8kg moving forwards at 5ms^-1. The bullet is embedded in the plasticine and the trolley moves at 8.5ms^-1. Calculate the velocity of the bullet before the impact.

Ans.: 475ms^-1

3. What is ‘completely inelastic collision’?

回答 (1)

Prof. Physics

2009-05-11 1:53 am

✔ 最佳答案

1.a. It is an inelastic collision.

Whenever there is a loss of energy to the surroundings from the system, which loses as internal energy or sound energy, the collision can be regarded as inelastic.

Now, the apple becomes warmer, which means there is a rise in internal energy. So, the collision is inelastic.

2. By the law of conservation of momentum

m1u1 + m2u2 = (m1 + m2)v

(0.006)u1 + (0.8)(5) = (0.006 + 0.8)(8.5)

Velocity of the bullet before impact, u1 = 475 ms-1

3. A completely inelastic collision refers to a collision in which the loss of mechanical energy of the system is the largest.

Usually, the lost of energy is half the total initial mechanical energy.

And it ofter happens whenever the two bodies embedded to each other after the impact.

參考: Physics king

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