Question Video: Finding the Momentum of an Object given Its Speed Mathematics

Determine the momentum of a car of mass 2.1 metric tons moving at 42 km/h.


Video Transcript

Determine the momentum of a car of mass 2.1 metric tons moving at 42 kilometers per hour.

We begin by recalling that the two factors that affect an object’s momentum are its mass and speed such that the momentum 𝐻 is equal to the mass 𝑚 multiplied by the speed 𝑣. In this question, we are told the mass of the car is 2.1 metric tons and its speed is 42 kilometers per hour. Substituting these values into the formula, we see that 𝐻 is equal to 2.1 tons multiplied by 42 kilometers per hour. To calculate 2.1 multiplied by 42, we can multiply two by 42 and then 0.1 by 42. These are equal to 84 and 4.2, respectively. As these two values sum to give us 88.2, 2.1 multiplied by 42 is equal to 88.2. We can therefore conclude that the momentum of the car is 88.2 ton kilometers per hour.

This is a slightly unusual unit as the standard unit of momentum is kilogram meters per second. However, any unit of mass multiplied by a unit of speed is a valid unit of momentum. Had we been required to give our answer in kilogram meters per second, we could’ve converted the mass to kilograms and the speed to meters per second before multiplying our values.

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