# Easy problem

1. Nov 13, 2009

### bmed90

I have to find the kenetic energy lost in the problem. I have both initial and final kenetic energy, how do i calculate the percent loss? I tried final over initial times 100 but that is not correct.

2. Nov 13, 2009

### PhanthomJay

How much KE is lost between the final and initial KE? That's the key in finding the percentage of the initial KE that is lost.

3. Nov 13, 2009

### bmed90

The answer is defenitaly negative, i know that

4. Nov 13, 2009

### PhanthomJay

if you have an initial KE of say 50 units and end up with a final KE of say 40 units, then the KE that is lost is__________ ??? Use that number as the numerator in your percent lost calculation.

5. Nov 13, 2009

### bmed90

Ok, so the change in kenetic energy over total kenetic energy multiplied by 100. Is that correct?

6. Nov 14, 2009

### bmed90

anyone?

7. Nov 14, 2009

### Cryphonus

Don't rush:).As phantom said above.You have to find the "loss" of energy between initial and final moments. As an initial value you have 50 units, at the end you have only 40 left.Calculate how much energy we lost here.After that its all Mathematics...

8. Nov 15, 2009

### bmed90

Yes, I get the difference in 10, but after I find the difference, what do I do? I know this is a simple question. I just don't remember how to do this.

9. Nov 15, 2009

### SeanGillespie

If you do lab reports in your science classes you will use the same formula to calculate the percentage error.

10. Nov 15, 2009

### bmed90

Well,, I am not trying to be a douche, but why cant anyone just say _____here is what you do______. Like I said I dont remember that is why I am posting this in the first place.

11. Nov 15, 2009

### SeanGillespie

You should make your own attempt, you will not learn if you do not try yourself. When it comes to an exam you won't have a forum to help you.

Post your attempts, at least you'll be putting your brain to use by trying, if you are wrong then you will be corrected.

12. Nov 15, 2009

### bmed90

Change/Initial....?

13. Nov 15, 2009

### bmed90

times 100

14. Nov 15, 2009

### bmed90

Well, I keep getting the wrong answer. That must not be right, but I could have sworn it is the right way to do this.