Kinetic energy lost during a collision?

[nips]

Homework Statement

A 1kg object traveling at 1 m/s collides head-on with a 2 kg object initially at rest. If the collision is completely inelastic, determine a) the velocity of the objects after impact and b) how much kinetic energy was lost during the collision.

Homework Equations

Part a) m1v1 + m2v2 = (m1+m2)v'
Part b) ke before =1/2m1v1^2, ke after= 1/2 (m1 + m2)v2^2

The Attempt at a Solution

Part a)
m1v1 + m2v2 = (m1+m2)v'
1 + 0 = 3(v')
v' = 1/3

Part b)
KE before: 1/2 m1v1^2
.5 (1)(1^2)
=.5
KE after: 1/2 (m1+m2)v2^2
.5(3)(0) = 0?

KE Lost:
(kinetic before - kinetic after)/kinetic before
(.5-0)/.5 = 1??

 

[Herman Trivilino]

did i do this right?

You have the system gaining energy! That can't be right. Check your figures.

Plus, you found the fractional loss, and you were asked for just the loss.

 

[ehild]

Homework Statement

A 1kg object traveling at 1 m/s collides head-on with a 2 kg object initially at rest. If the collision is completely inelastic, determine a) the velocity of the objects after impact and b) how much kinetic energy was lost during the collision.

Homework Equations

Part a) m1v1 + m2v2 = (m1+m2)v'
Part b) ke before =1/2m1v1^2, ke after= 1/2 (m1 + m2)v2^2

Explain what are v1, v2 and v'.

 

[Epic Mango]

The velocities you're using for kinetic energy are wrong; try to use the same variable names as with your momentum equation.