Set 4 Problem number 6

• Problem

• Solution

• Generalized Solution

Problem

The momentum of an object is -147 kg m/s. How fast is it moving if its mass is 21 kg?

Solution

Momentum is the product of mass and velocity.

It follows that if momentum and mass are known, velocity is momentum / mass.

• Dividing -147 kg m/s by 21 kg, we obtain the velocity

• v = -147 kg m/s / ( 21 kg) = -7 m/s.

Generalized Solution

Momentum p is the quantity that changes with impulse, the product mv of mass and velocity:

• p = m * v

Thus we easily find the velocity of an object of known mass if we know its momentum:

• v = p / m.