Question

A ball of mass 10 kg moving with a velocity of 10`sqrt3` ms^–1 along the X-axis, hits another ball of mass 20 kg which is at rest. After collision, the first ball comes to rest and the second one disintegrates into two equal pieces. One of the pieces starts moving along Y-axis at a speed of 10 m/s. The second piece starts moving at a speed of 20 m/s at an angle θ (degree) with respect to the X-axis.

The configuration of pieces after the collision is shown in the figure.

The value of θ to the nearest integer is ______.

Options

• 30

• 40

• 50

• 20

Answer 1

A ball of mass 10 kg moving with a velocity of 10`sqrt3` ms^–1 along the X-axis, hits another ball of mass 20 kg which is at rest. After the collision, the first ball comes to rest and the second one disintegrates into two equal pieces. One of the pieces starts moving along Y-axis at a speed of 10 m/s. The second piece starts moving at a speed of 20 m/s at an angle θ (degree) with respect to the X-axis. The configuration of pieces after the collision is shown in the figure. The value of the nearest integer is 30.

Explanation:

Before Collision

After Collision

Use momentum conservation along the X-axis.

`10 xx10sqrt3` = 20 cosθ × 10

 cosθ = `sqrt3/2`

 θ = 30°