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.) 0.5mv_1i²+0.5Mv_2i²=0.5mv_1f²+0.5Mv_2f²
Eq 2.) mv_1i+Mv_2i=mv_1f+Mv_2f

The Attempt at a Solution

I got v_2f=2 m/s and M=4 kg. I solved for M for the second equation and substituted that in into the first equation.

 

[ehild]

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.) 0.5mv_1i²+0.5Mv_2i²=0.5mv_1f²+0.5Mv_2f²
Eq 2.) mv_1i+Mv_2i=mv_1f+Mv_2f

The Attempt at a Solution

I got v_2f=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.

 

[fantisism]

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!

 

[ehild]

You are welcome