Question

A canon with a mass of 2,000 kg fires a 20 kg shell horizontally to the right with a velocity of 300 m/s. What is the recoil velocity of the cannon?

Answer 1

momentum of shell = mass × velocity

20 kg × 300 m/s = 6000 kg m/s
Rearrange the equation: velocity = momentum ÷ massvelocity of recoil on cannon = 6000 kg m/s ÷ 2000 kg = 3 m/s

Answer 2

Answer: - 3 m/s (the negative sign indiicates that it is in the opposite direction of shell.

Step-by-step explanation:

Data:

mass of cannon = 2000 kg
mass of shell = 20 kg
velocity of shell = 300 m/s
velocity of cannon = ?

Principles and formulas:

You have to use the momentum conservation law.

Initial momentum = final momentum

momentum = mass * velocity

Solution:

1) Initial momentum = 0

1) Final momentum = mass of the cannon * velocity of cannon + mass of the shell * velocity of the shell = 0

3) You know all the data except the velocity of the cannon. So clear it:

velocity of the cannon = - mass of the shell * velocity of the shell / mass of the cannon

4) Replacing the values known:

velocity of the cannon = - 20 kg * 300 m/s / 2000 kg = - 3 m/s.

The negative sign tells that the velocity of the cannon is in the opposite direction to the velocity of the shell.