- #1

TT0

- 211

- 3

## Homework Statement

A 20kg cannon ball is fired from a 600kg cannon, with an initial velocity of 450 m/s. Calculate the initial velocity of recoil of the cannon.

## Homework Equations

Conservation of momentum formula

m

_{1}u

_{1}+ m

_{2}u

_{2}= m

_{1}v

_{1}+ m

_{2}v

_{2}

where

m = mass

u = initial velocity

v = final velocity

## The Attempt at a Solution

m

_{1}u

_{1}+ m

_{2}u

_{2}= m

_{1}v

_{1}+ m

_{2}v

_{2}

let v = recoil velocity

20 x 0 + 600 x 0 = 20 x 450 + 600 x v

0 = 9000 + 600v

-9000 = 600v

v = -15 m/s

The negative is from the negative direction so the answer is 15 m/s. Is my logic correct, because I know how momentum is conserved, but is this the right way to think about it? Also how can Newton's law explain this?

Thanks