Part A You and your friend Peter are putting new shingles on a roof pitched at 2

Question

Part A You and your friend Peter are putting new shingles on a roof pitched at 22. You're sitting on the very top of the roof when Peter, who is at the edge of the roof directly below you, 5.5 m away, asks you for the box of nails. Rather than carry the 2.5kg box of nails down to Peter, you decide to give the box a push and have it slide down to him. If the coefficient of kinetic friction between the box and the roof is 0.55, with what speed should you push the box to have it gently come to rest right at the edge of the roof? Express your answer to two significant figures and include the appropriate units Value Units Submit My Answers Give Up Incorrect; Try Again; 24 attempts remaining Provide Feedback Continue

Explanation / Answer

perpendicular to plane

n - m*g*costheta = 0

normal force n = m*g*costheta

kinetic frictional force fk = uk*n = uk*m*g*costheta

along the incline

Fnet = m*g*sintheta - fk

Fnet = m*g*sintheta - uk*m*g*costheta

work done = Fnet*L

W = ( m*g*sintheta - uk*m*g*costheta)*L

from work energy theorem

work = change in KE = (1/2)*m*(vf^2 - vi^2)

(1/2)*m*(vf^2 - vi^2) = m*g*(sintheta - uk*costheta)*L

(1/2)*2.5*(0-vi^2) = 2.5*9.8*(sin22-(0.55*cos22))*5.5

initial speed vi = 3.82 m/s <<<------------ANSWER

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