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Secure httpsillsession masteringphysics.com/myct/ltemview?assignmentProblemID et next signed in as yasmin ibrahim Coin PHY116W2017PEIRIS Hoe Chapter UneorMomentum. Con Problem 7.71 e previous l 15 of 16 I next Problem 7.71 Part A lf the coeficient of kinetic friction between the block and the surface is o.25, and the impact drives the A 25 g bullet strikes and becomes embedded in a block a distance of 9.9 m before it oomes to rest, what was the muzzle speed of the bullet? 1.30 kg block of wood placed on a horizontal Sunday surface just in front of the gun. Express your answer using two significant figures. Submit My Answers Give Up Provide Feedback Continue MacBook Pro

Explanation / Answer

Using Force balance

Ff = u*(M+m)*g

Using energy conservation:

KEi + PEi + Wf = KEf + PEf

PEi = PEf = 0

KEi = 0.5*(M+m)*V^2

KEf = 0

Wf = -Ff*x = -u*(M+m)*g*x

0.5*(M+m)*V^2 = u*(M+m)*g*x

V = sqrt (2*u*g*x)

V = sqrt (2*9.81*9.9*0.25) = 6.97 m/sec

Now using momentum conservation

Pi = Pf

m*v1 + M*v2 = (M+m)*V

v1 = speed of bullet initially

v2 = 0 = speed of wood initially

v1 = (M+m)*V/m

v1 = (0.025 + 1.3)*6.97/0.025 = 369.41 m/sec

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