Question

A girl of mass 50kg jumps out of a rowing boat of mass 300kg on to the bank,with a horizontal velocity of 3m/a. with what velocity does the boat begin to move backwards?​

Answer 1

m1=50 kg

m2=300 kg

v1= 3 m/s

v2=?

we have to find.

conservation of momentum=m1+v1+m2v2+0

0 is because no initial velocity is applied and the answer will be 

50 x 3 + 300v2=0

i.e v2 = -150/300=-0.5m/s

so it is moving backward direction the velocity (v2) will be 0.5m/s in the backward direction.

Answer 2

Answer:

Initial Momentum = Final momentum

0 = m1u1 + m2u2

u2 = -(m1 u1) / m2

= -(50 kg × 3 m/s) / (300 kg)

= -0.5 m/s

(-ve sign indicates that boat moves backwards)

Velocity of boat will be 0.5 m/s (ans)