# Collision with an unknown mass and velocity after

• fantisism

## Homework Statement

You slide a 2 kg block on a flat icy surface towards a static block of mass M. Before the collision, the 2 kg mass is moving at 3 m/s. The total kinetic energy is not changed by the collision. After the collision, the 2 kg mass is moving at −1 m/s i.e. opposite to its original direction. Calculate the mass M in kg and the velocity of the mass M after the collision.

## Homework Equations

Eq 1.) 0.5mv1i2+0.5Mv2i2=0.5mv1f2+0.5Mv2f2
Eq 2.) mv1i+Mv2i=mv1f+Mv2f

## The Attempt at a Solution

I got v2f=2 m/s and M=4 kg. I solved for M for the second equation and substituted that in into the first equation.

## Homework Statement

You slide a 2 kg block on a flat icy surface towards a static block of mass M. Before the collision, the 2 kg mass is moving at 3 m/s. The total kinetic energy is not changed by the collision. After the collision, the 2 kg mass is moving at −1 m/s i.e. opposite to its original direction. Calculate the mass M in kg and the velocity of the mass M after the collision.

## Homework Equations

Eq 1.) 0.5mv1i2+0.5Mv2i2=0.5mv1f2+0.5Mv2f2
Eq 2.) mv1i+Mv2i=mv1f+Mv2f

## The Attempt at a Solution

I got v2f=2 m/s and M=4 kg. I solved for M for the second equation and substituted that in into the first equation.
What is your question then? That result is correct.

What is your question then? That result is correct.
Oh sorry. I just wanted to make sure those were right because I tend to make small simple math errors. Thank you!

You are welcome