1. ## Physics question (elasticity)

What is the elasticity of a ball which hits a wall at 10 m/s and rebounds off the wall at 8 m/s? (answer to 2 significant digits)

That's an online question for school. All of us trying to do it can't get it. It should be 80% I think, but it's not. And it's not a multiple choice question.

Anyone know how you would do that?

2. 5.

3. What....? 5 is the answer? Huh? I can't make sense out of that...and it should be a two digit number (yes I know how sig figs work but I know that what my teacher implies by that)

4. 64%

5. 8.0x10^-1

6. Originally posted by ZerOrDie
64%
How'd you get that?

7. 3X

Now just have to solve for X.

8. e = ( 1 - ((EKInitial - EKFinal) / EKInitial)) *100 = x%

We will substitute any mass. Lets say 1kg.

EK = (1/2)mv^2

EKInitial = (1/2)(1)(10)^2 = 50J
EKFinal = (1/2)(1)(8^2) = 32J

((50 - 32) / 50) * 100 = 36%

1 - .36 = .64
.64 * 100 = 64%

The ball has an elasticity of 64% (as 36% of the Kinetic energy was lost). Just remember your conservation of energy.

9. looks like someone took the time to explain my answer lol

10. Originally posted by ZerOrDie
looks like someone took the time to explain my answer lol
Yes. I had to look back on some previous work because I realized that I actually forgot how to calculate the elasticity of an object - which frusterated me to no end.

11. im so mad. I even tried that, but it said it was incorrect so I reverted to 80%! I think it has problems with how you enter the answer, like it'd make a difference if it was 64, 64%, or 64 %

That threw me off then, indeed!

12. Try .64