Question

A 3kg ball moving at 8 m/s strikes a 2kg ball at rest,if the collision is elastic,what is the speed of the lighter ball if the heavier ball moves at 2m/s in the opposite direction

Answer 1

Speed of lighter ball is 4 m/s.

Step-by-step explanation:

Applying the principle of conservation of linear momentum,

momentum before collision = momentum after collision.

`m_(1)`
`u_(1)` +
`m_(2)`
`u_(2)` =
`m_(1)`
`v_(1)` -
`m_(2)`
`v_(2)`

`m_(1)` = 3 kg,
`u_(1)` = 8 m/s,
`m_(2)` = 2 kg,
`u_(2)` = 0 m/s ( since it is at rest),
`v_(1)` = 2 m/s,
`v_(2)` = ?

(3 x 8) + (2 x 0) = (8 x 2) - (2 x
`v_(2)`)

24 + 0 = 16 - 2
`v_(2)`

2
`v_(2)` = 16 - 24

2
`v_(2)` = -8

`v_(2)` =
`(-8)/(2)`

= -4 m/s

This implies that the light ball moves at the speed of 4 m/s in the opposite direction of the heavier ball after collision.