How Much Work Does the Wall Do to Stop a Skater?

[ash4741]

Wall excerts work on skater: Please help :(

Homework Statement

A 69.0-kg short-track ice skater is racing at a speed of 11.0 m/s when he falls and slides into a padded wall that brings him to rest. Assuming that he does not lose any speed during the fall or while sliding across the ice, how much work is done by the wall while stopping the ice skater?

Homework Equations

Ke=1/2mV^2
W=1/2m(Vf^2+Vi^20
W=Fdcos()
F=ma or F=mg

The Attempt at a Solution

I am not sure what I am doing. I attached an image of my work.

 

[PhanthomJay]

Homework Statement

A 69.0-kg short-track ice skater is racing at a speed of 11.0 m/s when he falls and slides into a padded wall that brings him to rest. Assuming that he does not lose any speed during the fall or while sliding across the ice, how much work is done by the wall while stopping the ice skater?

Homework Equations

W=1/2m(Vf^2+Vi^20

is this the work-energy theorem equation? It's not correct, but this one looks like the one to use, once corrected. Can't see your work yet, though.

 

[ash4741]

W=1/2m(Vf^2+Vi^2)
W=1/2(69)(0^2+11^2)
W=1/2(69)(121)
W=34.5(121)
W=4174.5
This is wrong answer.

 

[PhanthomJay]

W=1/2m(Vf^2+Vi^2)
W=1/2(69)(0^2+11^2)
W=1/2(69)(121)
W=34.5(121)
W=4174.5
This is wrong answer.

check your work energy equation again; it is incorrect. And don't forget the units.

 

[Jdo300]

Check here for information on work energy equations:

http://hyperphysics.phy-astr.gsu.edu/hbase/work.html#wepr

- Jason O

 

[ash4741]

W=1/2mVf^2-1/2mVi^2
W=1/2(69)(0)-1/2(69)(121)
W=-4174.5 J

 

[PhanthomJay]

Looks good now!

 

[ash4741]

Thanks ^^