Question

a monkey of mass 20 kg rides on a 40 kg trolly moving with constant speed of 8 m/s along a horizontal track. if the monkey jumps vertically to grab the overhanging branch of a tree , the speed of the trolley after the monkey has jumped off is

Answer 1

according to law of conservation of momentum ,
m1v1=m2v2
(20+40)×8=40×v2
(60×8)/40 = V2
thus, v2=12 m/s

Answer 2

Given that monkey jumps vertically upward that means there is no horizontal force on trolly.

So there is no force in horizontal direction which can decrease or increase the velocity of that trolley.

Thus speed of that trolley will remain same.

Speed of that trolley will remains 8 m/s only.

Here masses are given only for confusion.

If you still have any doubt then you can comment me...

"Thanks"