Question

Conservation of momentum in a collision between particles can be understood from ______.

Options

• Conservation of energy.

• Newton’s first law only.

• Newton’s second law only.

• Both Newton’s second and third law.

Answer 1

Conservation of momentum in a collision between particles can be understood from both Newton’s second and third law.

Explanation:

By Newton’s second law of motion, we can write `(dP)/(dt) = F_(ext)`

Since by the law of conservation of momentum, we have `F_(ext)` = 0

Therefore, `(dp)/(dt)` = 0

Hence momentum is constant.

Also by Newton’s third law of motion, we have `F_12 = - F_21`

`(dp_12)/(dt) = - (dp_21)/(dt)` 

⇒ `dp_12 = - dp_21`

That gives `dp_12 + dp_21` = 0

Here the law of conservation of momentum is proved.