A 950 kg car moves at 18 m/s. Its brakes give a steady force of 5700 N against the motion…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A car moves at . Its brakes give a steady force of against the motion.
- In what distance does it stop?
- What would the distance be at , with the same braking force?
Need a reminder? The key ideaShow
Kinetic energy is . The work-energy theorem: the net work done on a body equals its change in kinetic energy, .
The worked solution
Have you tried it?
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.
Given. , , .
Plan. .
Step 1. Kinetic energy. .
Step 2. Distance. .
Step 3. Twice the speed. Four times the energy, so four times the distance: .
Answer: (a) . (b) .
Check. With , . It agrees.
Watch out. Doubling the speed does not double the stopping distance. It multiplies it by four.
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