# A 23 g bullet traveling 220 m/s penetrates a 2.3 kg block of wood and emerges cleanly at 180 m/s....

## Question:

A {eq}23 \ g {/eq} bullet traveling {eq}220 \ \frac{m}{s} {/eq} penetrates a {eq}2.3 \ kg {/eq} block of wood and emerges cleanly at {eq}180 \ \frac{m}{s} {/eq}.

If the block is stationary on a frictionless surface when hit, how fast does it move after the bullet emerges? Express your answer using two significant figures.

## Conservation of Linear Momentum:

Linear momentum {eq}p {/eq} is defined as the mass of an object times its velocity. It is a vector that points in the same direction as velocity.

{eq}\vec p = m\vec v {/eq}

Momentum is measured in kilogram-meters per second, or {eq}\frac{kgm}{s} {/eq}.

Momentum is a useful quantity because it is conserved for a closed system (in which there are no external forces present). This means that we can measure the total momentum of a system at two different times (adding up each object's momentum, following the rules of vector addition) and our answers will be the same. The total momentum cannot increase or decrease over time.

We can use conservation of momentum to solve this problem. We know that the total initial momentum must be equal to the total final momentum:

{eq}p_i...

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