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## Conservation of linear momentum – Problem

Astronauts Mr.X and Mr.Y float in a zero gravity space with no relative velocity to one another. Mr. Y throws a mass of 5 kg towards X with speed 2 m/s. If Mr. X catches it, the change in velocity of X and Y are (choose the correct option)

(a) 0.21 m/s, 0.80 m/s

(b) 0.80 m/s, 0.21m/s

(c) 0.12 m/s, 0.08 m/s

(d) 0.08 m/s, 0.12 m/s

Please provide me the solution part step by step

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## Problem from relative velocity

A Boat covers certain distance between two spots in a river taking t1 hrs going downstream and t2 hrs going upstream. What time will be taken by boat to cover same distance in still water?

posted by STUTI

Answer:

## Relative velocity in free fall

If a person jumps out of a plane, and a few seconds later, another person jumps, why is it that the difference in their velocities stays the same? Shouldn’t it decrease because eventually, the first diver will reach maximum velocity, but the other diver will be slower at first, but then he reaches max. velocity as well…I’m not wording it the best way, but any help would be greatly appreciated :]

[Posted by Iris]

Both are examples for free fall. The velocity at any instant is given by v = gt

If for the first one, time = t and for the second who jumps after n seconds, time=t-n

Therefore, velocity of the first one at any instant, v1=gt

for second one, v2=g(t-n)

The difference in velocities,

v1-v2 = gn, which shows that the difference in velocity remains constant.

This is because, both are moving with the same acceleration and their velocities are increasing at the same rate