# Homework Help: Kinetic Energy and Momentum

1. Nov 21, 2004

### pinky2468

This is a question from a practice test, so it might also be a test question. For some reason I am tripping myself up on it:

A space vehicle mas m has a speed v. At some instant, it separates into two pieces each of mass 0.5m. One of the pieces is at rest just after the separation.
(A) Does this process:
(a)conserve kinetic enery (b)not conserve total enery (c) the moving piece has a speed 2v (d) not conserve momentum

(B)what is the KE of the moving piece just after the separation:
(C) how much work was done by the internal forces that caused the separation:

For part B and C the multiple choice answers are the same
(a.) 0 J (b). 1/4mv^2 (c.)1/2mv^2 (d.) mv^2 (e.) 2mv^2

Any help on this, my first thought were that (A) the speed is 2v (B) 2mv^2 (C) ? not sure

2. Nov 21, 2004

### gnome

Think about this: which is a vector quantity, energy or momentum?

3. Nov 21, 2004

### stunner5000pt

Consider that piece that now has the velocity 2v what was its initial velocity

using the work -energy theorem,

$$W = \Delta K$$

that your answer for C

your answers for A and B are fine

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