# Kinetic Energy problem i think

nlsed

## Homework Statement

What takes more energy? Accelerating a car from 10-20m/s or from 20-30m/s? Why?

## The Attempt at a Solution

Since KE = 1/2mv^2, I suppose the higher the velocity is the more kinetic energy the car will have, but I have no clue how to solve this problem.

## Answers and Replies

Homework Helper
Won't the bigger change in kinetic energy require the greater energy?
You know that conservation of energy thing?

Plug in the numbers.

lubuntu
then change in kinetic energy equals the work done, which one requires more work?

nlsed
so is this right? since m is constant it is just 1kg

1/2mv2
1/2(1kg)(10m/s)2 = 50 joules
1/2(1kg)(20m/s)2 = 200 joules
1/2(1kg)(30m/s)2 = 450 joules

KE for (10-20m/s) = 150 joules
KE for (20-30m/s) = 250 joules

So accelerating from 20-30m/s requires 100 more joules of energy?

Last edited:
Homework Helper
So accelerating from 20-30m/s requires 100 more joules of energy?

That should do it.

nlsed
Thank you very much!!! :!!)