Set 4 Problem number 7

• Problem

• Solution

• Generalized Solution

Problem

An object moving at 9 m/s has momentum 216 kg m/s?   What is its velocity?

Solution

An object with velocity 9 m/s has momentum 216 kg m/s, and we are to find its mass.

• Since momentum is the product of mass and velocity, the mass is the momentum divided by the the velocity.
• The mass is thus m = p / v = ( 216 kg m/s)/( 9 m/s) = 24 kg.

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 mass of an object of known velocity if we know its momentum:

• v = p / m.