A mini van has a momentum of 1,420 kg*m/s. If it is traveling at 44 miles per hour, what is the scooter's mass?

Question

A mini van has a momentum of 1,420 kg*m/s. If it is traveling at 44 miles per hour, what is the scooter's mass? Report your answer to 1 decimal place. Please do not include units or the answer will be marked incorrect.

Answer 1

Momentum (kg*m/s) = mass (kg) * velocity (m/s)

We are given the momentum and velocity. Rearranging the equation to solve for mass, we get:

mass (kg) = momentum / velocity

Our momentum is given to us in metric units, so let's first convert 44 miles per hour (mph) to meters per second (m/s). We're going to multiply the given velocity by a set of conversion factors to get meters per second.

44 miles/hour * 1.61 kilometer/mile = 70.81 kilometers/hour

70.81 kilometers/hour * 1000 meters/kilometer = 70811 meters/hour

70811 meters/hour * 1 hour / 3600 seconds = 19.67 meters/second

Now we can solve our equation for mass

mass (kg) = momentum / velocity = (1420 kg*m/s) / (19.67 m/s) = 72.2 kg = mass of the minivan

To double check our work, it's important that we pay attention to the units of each value and that we're getting the correct units for our answer. Using the above equation, we find that the m/s cancels out in the fraction, leaving us with kg, the correct unit for mass.