Question

A car weighing 14000 N is speeding down the highway at 80 km/h. What is its momentum?

Answer 1

The momentum is defined as:

`p=mv`

In this case we know the velocity but we don't know the mass yet. The weight of an object is given by:

`\begin{gathered} W=mg \\ \text{ Then} \\ m=(W)/(g) \end{gathered}`

Then we can express the momentum as:

`p=(W)/(g)v`

before we plug the values of the weight and the velocity in our expression we need to convert the velocity to m/s:

`80(km)/(h)\cdot\frac{1000\text{ m}}{1\text{ km}}\cdot\frac{1\text{ h}}{3600\text{ s}}=22.22(m)/(s)`

Now that we have the velocity we plug it with the weight to find the momentum:

`\begin{gathered} p=(14000)/(9.8)(22.22) \\ p=31746.03 \end{gathered}`

Therefore, the momentum is 31746.03 kg m/s