Question

A body of mass M collides against a wall with velocity V and rebounds with the same speed. It's change of momentum is

Answer 1

No Change as such

Answer 2

momentum= mass*velocity
both remain same after collision
so no change in momentum.

Answer 3

Answer is given as 2MV

Answer 4

But how? Are we to add both the momenta?

Answer 5

adarsh see the direction change as well
first it is +v next it is -v

Answer 6

Okay. yeah, got it.
First, Its MV. Second is -MV. Subtracting, we get 2MV.

Answer 7

By subtracting how we get 2MV

Answer 8

But I don't understand why the sign is +ive in first case and -ive in second case.

Answer 9

See, MV - ( - MV) = MV + MV = 2MV(Simple integer addition)

Answer 10

Can anyone say about the signs?

Answer 11

because we shud maintain a standard sign system like think this way