Homework Help: Physics

Posted by Mary on Monday, April 9, 2012 at 8:20pm.

A bullet mass 10 g strikes a log with a mass of 25 g suspended from a 3 meter long string. The bullet lodges in the log which swings up through an angle of 30 degrees. Find the speed of the bullet just before it hit the log.

Physics - Elena, Tuesday, April 10, 2012 at 11:08am
The law of conservation of linear momentum
m•v = (m +M) •u.
v =(m +M) •u/m.
The law of conservation of energy
KE =PE,
(m+M) •u^2/2 =(m+M) • g•h,
u = sqrt (2•g•h).
Since h =L(1-cosα) ,
v =[(m +M) /m] • sqrt[2•g•L(1-cosα)].

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