A rifle bullet of mass m = 2.5 g traveling at vb = 243 m/s collides with and embeds itself in a pendulum of mass M = 237.5 g, initially at rest and suspended vertically with massless strings of length L = 2 m.(adsbygoogle = window.adsbygoogle || []).push({});

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i first converted the masses into kilograms.

i found out that net momentum = 0.6075 kg m/s, for the bullet-pendulum mass of 0.24kb. that means that the pendulum moves at first with v = 2.53125.

now... where do i go from here?

i don't even know the angle at which the bullet-pendulum combination reaches the max height. if i knew, it would be 2*tan(theta).

so i guess the challenge is to find the angle at which the thing goes at its max height...? bleh.. i'm lost

edit:

by the energy equation, i guess...

for M = total mass, 1/2*Mv(f)^2 + Mgy(f) = 1/2*Mv(i)^2 + Mgy(i)

y(i) is zero, so the last term cancels out.

v(f) is zero, so the first term cancels out.

Mgy(f) = 1/2*Mv(i)^2

y(f) = Mv(i)^2 / (2Mg)

i get 0.6538, which is not the answer...

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# Homework Help: Ballistic Pendulum

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