Question

. A man weighing 60 kg runs along the rails with velocity of 18km/hr and

jumps into a car of mass 1 quintal standing on the rails. Calculate the velocity

with which car will start travelling along the rails​

Answer 1

Explanation:

Mass of man = 60kg = m1

Mass of car = 1 quintal = 100kg = m2

Initial velocity of man = 18km/hr = u1

(As, 1km = 1000m and 1hr = 3600s

18km/hr =

= 5m/s )

Final velocity of man = v = v1

Initial velocity of car = 0m/s = u2

Final velocity of car = v = v2

v1 = v2 = v as the final velocity is combined for both man and car.

As the momentum is conserved.

According to Law of Conservation of Momentum

m1u1 + m2u2 = m1v1 + m2v2

60kg × 5m/s + 100kg × 0m/s = 60kg × v +100kg × v

300kgm/s + 0kgm/s = 60v + 100v

300kgm/s = 160v

300/160 = v

1.875m/s = v