Question

A simple way to measure the speed of a bullet is with a ballistic pendulum. It consist of a block of mass $m_{p}$ suspended by a cable of length 'L' and swings an angle $\phi$ due to the bullet. the bullet has a mass $m_{b}$ and initial velocity $V_{0}$. The bullet is completely absorbed by the block, and there is no external force so momentum is conserved.

a) Why is Energy NOT conserved?

b) Once the bullet is lodged in the block, energy is now conserved. Find the bullet velocity given $m_{p}$ / $m_{b}$, L, and $\phi$.

c) Find how much energy is lost in the block.

Answer 1

(a) every does not remains conserved in inelastic collision because when bullet enters in block some part of it converted into thermal energy (b) conservation angular momentum m_b v_0 L + 0 = (m_b + m_O) L^2 w w = V/R = V/L m_b v_0 = (m_b + m_o) v/t v = m_b v_o/(m_b + m_o) = final velocity after just collision of bullet Block combined system Now after bullet enters in block v = squareroot 2 gh L minus h/L = cos phi h = L{1 minus cos phi} V = squareroot 2 gl (1 minus cos phi)