Q.4 A horizontal force of 100 N is applied by a person to push a 40 kg packing c
ID: 1785835 • Letter: Q
Question
Q.4 A horizontal force of 100 N is applied by a person to push a 40 kg packing crate a distance of 4m on a rough horizontal surface. If the crate moves at constant speed, find a) the work done by the person and b) the coefficient of kinetic friction between the crate and the surface. Q.5 A 0.02kg bullet is fired at a muzzle velocity of 582 m/s from a gun with a mass of 8kg and barrel length of 0.75 m. The bullet was in the barrel for 0.07 sec. B) What is he force on the bullet while it is in the barrel? C) Find the impulse exerted on the ullet while it is in the barrel? D) Find the bullet's momentum as it leaves the barrel? 40 points) Yl: Muzzle velocity is the velocity at the end of the barrel.Explanation / Answer
4. (A) work done = F.d = F d cos(theta)
work done by person, Wp = (100)(4) cos0 = 400 J
(b) change in KE = 0 so net work done = 0
hence work done by friction = - 400 J
f = 400 / 4 = 100 N
f = u m g
u = 100 / (40 x 9.81) = 0.25 .......Ans
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