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Kinetic Energy problem... i think..

by nlsed
Tags: energy, kinetic
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nlsed
#1
Mar4-09, 06:56 PM
P: 10
1. The problem statement, all variables and given/known data

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

2. Relevant equations



3. 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.
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LowlyPion
#2
Mar4-09, 07:33 PM
HW Helper
P: 5,343
Won't the bigger change in kinetic energy require the greater energy?
You know that conservation of energy thing?

Plug in the numbers.
lubuntu
#3
Mar4-09, 07:36 PM
P: 473
then change in kinetic energy equals the work done, which one requires more work?

nlsed
#4
Mar4-09, 07:40 PM
P: 10
Kinetic Energy problem... i think..

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?
LowlyPion
#5
Mar4-09, 08:15 PM
HW Helper
P: 5,343
Quote Quote by nlsed View Post
So accelerating from 20-30m/s requires 100 more joules of energy?
That should do it.
nlsed
#6
Mar4-09, 08:34 PM
P: 10
Thank you very much!!!


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