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A 20.0 kg wood ball hangs from a 1.50 m-long wire. The maximum tension the wire can withstand without breaking is 300 N. A 0.900 kg projectile traveling horizontally hits and embeds itself in the wood ball.

What is the largest speed this projectile can have without causing the cable to break?

What I have tried:

I tried to use the tension formula (T = mv^2/r) along with the conservation of momentum formula.

First I tried:

v = sqrt(Tr/m) = sqrt(300*1.5/20) = 4.74

and then m1v1 = m2v2 = mfvf

so .9v = 20.9 *4.74 = 110.2 m/s which was wrong

then I tried:

v = sqrt(Tr/m) = sqrt(300*1.5/20.9) = 4.64

so .9v = 20.9 * 4.64 = 107.8, which is also wrong

Can anyone point out where I'm making a mistake? I think the theory is sound, but I cant figure out where I'm going wrong.

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# Homework Help: Conservation of momentum and wood ball problem

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