Question

A man weighing 60 kg runs along the rails with a velocity of 18 km/h and jumps into a car of mass 1 quintal (100 kg) standing on the rails. Calculate the velocity with which the car will start travelling along the rails.

CBSE Class IX Science SA 2 (3 Marks)

Answer 1

Mass of man m₁ = 60 kg, Initial velocity of mass u₁ = 18 km/h = 5 m/s

Mass of car m₂ = 100 kg, Initial velocity of car u₂ = 0

After the man jumps into the car, let their common velocity be V.

Applying the law of conservation of momentum,

Total momentum after jump = Total momentum before jump

(m₁ + m₂) V = m₁u₁ + M₂ U₂

(60 + 100) V = 60 x 5 + 100 x 0

160 V = 300;

V = 300/160

V = 1.875 m/s

The velocity is 1.875 m/s.