A 950 kg car moves at 18 m/s. Its brakes give a steady force of 5700 N against the motion…

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A $950\ \text{kg}$ car moves at $18\ \text{m/s}$ . Its brakes give a steady force of $5700\ \text{N}$ against the motion.

In what distance does it stop?
What would the distance be at $36\ \text{m/s}$ , with the same braking force?

Need a reminder? The key ideaShow

Kinetic energy is $K = \tfrac12 mv^2$ . The work-energy theorem: the net work done on a body equals its change in kinetic energy, $W_{\text{net}} = \tfrac12 mv^2 - \tfrac12 mu^2$ .

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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