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Questions & Answers

"A car driver has to make an emergency stop. The braking distance depends on the speed of the car. For the same braking force, what happens to the braking distance if the speed doubles?"

To understand this, we have to take it step by step. Firstly, if the speed is doubling, then that means kinetic energy increases by a factor of 4, since:

K.E = 12mv2 therefore K.E  v2
So 2v leads to (2)2K.E = 4K.E

Now that kinetic energy has increased by a factor of 4, the car has to do more work to slow down to a stop.

Since W = F x d, therefore W  d
So 4W leads to 4d

Therefore, braking distance d increased by a factor of 4 as well!

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