Physics problem, basketball dunk (Hookes law)

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A 95 kg basketball player slams down and hangs on the rim, which has a spring constant of 7400 N/m. The problem requires calculating how much the rim bends when the player hangs on it, focusing on static equilibrium rather than dynamic motion. The correct approach involves using the formula for spring extension, leading to the conclusion that the rim bends approximately 0.15 m, as stated in the textbook. The confusion arises from misapplying kinetic energy concepts, as the problem is primarily about static forces. The key takeaway is that the extension of the rim under a static load can be determined without considering kinetic energy.
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Homework Statement


A 95kg basketball player slam dunks a basketball and hangs onto the rim. Find out how much the rim bends if its spring constant = 7400 N/m and the basketball rim is 2 m in the air.

Homework Equations


Ep = 0.5 k x^2
Ek = 0.5 m v^2
Eg = mgh

The Attempt at a Solution


The book got 0.15 m. My answer is way off, what did I do wrong? I think this should be right.

Ep1 + Ek1 + Eg1 = Ep2 + Ek2 + Eg2
Ep1 = 0, Ek1 = 0, Ek2 = 0

Eg1 = Ep2 + Eg2
mgh = (1/2)kx^2 + mg(2m - x)

1862 J = 3700x^2 N/m + 1862 J - 931x N

3700x^2 N/m - 931x N = 0

931x N( 3.97x / m - 1 ) = 0

x = 0 or 3.97x/m = 1

x = 1/(3.97/m) = 0.25 m.

Book got 0.15. My answer is way off and I'm not sure why it could be look this. Is my logic correct? Am I correct?
 
Last edited:
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It is not entirely clear, but I don't think it is asking the maximum extent of the bend under SHM. It's a statics question: if the player hangs on for an arbitrarily long time, what will the extent of the bend settle out at?
 
You are not given any speeds so there is no point in looking at kinetic energy. The problem is just "if a 95 kg object is hung from a spring with spring constant 7400 N/m, how far will the spring extend?"

95g=
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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