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)].
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.
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