Question

A girl of mass 40 kg jumps with a horizontal velocity of 5 m/s onto a cart of mass 10kg with friction less wheels, which is already moving with a horizontal velocity 1 m/s in the opposite direction of motion of the girl. What will be the velocity of the girl, when the cart moves along with her. (Assume that there is no external unbalanced force working in the horizontal direction) ANSWER PLS!!!!!!

Answer 1

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law of conservation of momentum.

mass of girl(m1) = 40 kg

initial velocity of girl(u1) = 5m/s

mass of cart(m2) = 10 kg

initial vel. of cart(u2) = 1m/s

final velocity of combined system(v) = ?

see, it is a combined system because the girl came on the cart so their velocity would be same.

m1u1 +m2u2 = m1v +m2v

40*5 + 10*1 = (m1+m2)v                  #took v as common

200 + 10 = (40+10)v

210 = 50v

v = 21/5

   = 4.2 m/s ans.

hope it helps!

Answer 2

if there is no fnet on system then momentum is conserved. pls note that velocity must be put wirh direction and all the velocity must be with respect to ground.