Question

A bullet of mass 20 g traveling horizontally with a speed of 500 m/s passes through a wooden block of mass 10.0 kg initially at rest on a level surface. The bullet emerges with a speed of 100 m/s and the block slides 20 cm on the surface before coming to rest. Find the friction coefficient between the block and the surface. (Figure 9-E13).

Answer 1

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ANSWER::

Mass of bullet , m = 0.02 kg

Initial velocity of bullet , v₁ = 500 m/s

Mass of block , M = 10 kg

Initial velocity of block , v₂ = 0

Final velocity of bullet , v₁' = 100 m/s

Let the final velocity of block when bullet comes out , if block = v'

mv₁ + Mv₂ = mv₁' + Mv'

0.02 x 500 = 0.02 x 100 + 10 x v'

v' = 0.8 m/s

After moving a distance 0.2 m it stops .

Change in Kinetic Energy = Work done

0 - (1/2) x 10 x (0.8)² = -μ x 10 x 10 x 0.2

μ = 0.16

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