A body of mass 10 kg moving at a speed of 4 m/s collides with another body of mass 4 kg at rest. After collision, if the speed of the body of 4kg mass be 5 m/s, the speed of body of 10kg mass shall be?

momentum before = momentum after

4*10 = 4*5 + 10*x

To find the speed of the body with a mass of 10 kg after the collision, we can use the law of conservation of momentum.

According to the law of conservation of momentum, the total momentum before the collision is equal to the total momentum after the collision. Momentum is defined as the product of mass and velocity.

Before the collision:
Momentum of the 10 kg mass: 10 kg × 4 m/s = 40 kg·m/s (since it is moving)
Momentum of the 4 kg mass: 4 kg × 0 m/s = 0 kg·m/s (since it is at rest)

After the collision:
Let's assume the final velocity of the 10 kg mass is v m/s.

Momentum of the 10 kg mass: 10 kg × v m/s = 10v kg·m/s
Momentum of the 4 kg mass: 4 kg × 5 m/s = 20 kg·m/s

According to the law of conservation of momentum, the total momentum before the collision is equal to the total momentum after the collision.

Total momentum before collision = Total momentum after collision
40 kg·m/s + 0 kg·m/s = 10v kg·m/s + 20 kg·m/s

Simplifying the equation:
40 kg·m/s = 10v kg·m/s + 20 kg·m/s
40 kg·m/s - 20 kg·m/s = 10v kg·m/s
20 kg·m/s = 10v kg·m/s

Dividing both sides by 10 kg·m/s:
20 kg·m/s / 10 kg·m/s = 10v kg·m/s / 10 kg·m/s
2 m/s = v

Therefore, the speed of the body with mass 10 kg after the collision is 2 m/s.