Elastic Collision: Contact Time?

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The discussion revolves around calculating the contact time of a handball with a wall after being thrown and rebounding. The initial calculations incorrectly considered the change in velocity (Δv) as zero, leading to an erroneous result of 0 seconds for contact time. Participants emphasized the importance of accounting for direction in the velocity change, which ultimately corrected the misunderstanding. After addressing the calculation error, the correct approach yielded a valid solution. The thread highlights the significance of proper vector analysis in physics problems.
Psych Berry
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Homework Statement


A handball of mass 668 grams is thrown straight against a wall with a speed of 13.36 m/s. It rebounds straight back out with the same speed. The average force exerted on the wall by the ball is 12 N.

How long is the ball in contact with the wall?


Homework Equations


FΔt = mΔv (?)


The Attempt at a Solution


m = 0.668 kg, Δv = 0 m/s, F = 12N
With the equation I used, the answer I get is 0 s, but the answer isn't 0 s.

Can anyone tell me what the correct equation to use is? Or what I'm doing wrong?
 
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You are calculating Δv incorrectly. Don't forget to take direction into account.
 
Doc Al said:
You are calculating Δv incorrectly. Don't forget to take direction into account.

Thank you! That should have been so obvious. I got it right this time.
 
Thread 'Correct statement about size of wire to produce larger extension'

Thread 'Correct statement about size of wire to produce larger extension'

The answer is (B) but I don't really understand why. Based on formula of Young Modulus: $$x=\frac{FL}{AE}$$ The second wire made of the same material so it means they have same Young Modulus. Larger extension means larger value of ##x## so to get larger value of ##x## we can increase ##F## and ##L## and decrease ##A## I am not sure whether there is change in ##F## for first and second wire so I will just assume ##F## does not change. It leaves (B) and (C) as possible options so why is (C)...
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