A 100-kg cannon at rest contains a 10-kg cannon ball. When fired, the cannon ball leaves the cannon with a speed of 90 m/s. What is the recoil speed of the cannon?

The recoil speed of the cannon is 9 m/s

Explanation:

Here momentum is conserved,

Initial momentum = Final momentum

Since the system is in rest initially initial momentum is zero,

So we have

Final momentum = 0

Momentum of cannon + Momentum of cannon ball = 0

Mass of cannon = 100 kg

Mass of cannon ball = 10 kg

Speed of cannon ball = 90 m/s

100 x Speed of cannon + 90 x 10 = 0

100 x Speed of cannon = - 900

Speed of cannon = - 9 m/s

The recoil speed of the cannon is 9 m/s