Starting from rest, a 4.80-kg block slides 2.00 m down a rough 30.0° incline. The coefficient of kinetic friction between the block and the ?

Starting from rest, a 4.80-kg block slides 2.00 m down a rough 30.0° incline. The coefficient of kinetic friction between the block and the incline is

μk = 0.436.

(a) Determine the work done by the force of gravity.

 J

(b) Determine the work done by the friction force between block and incline.

 J

(c) Determine the work done by the normal force.

 J

(d) Qualitatively, how would the answers change if a shorter ramp at a steeper angle were used to span the same vertical height?

1 Answer

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  • oubaas
    Lv 7
    2 months ago

    (a)

    Determine the work W done by the force of gravity

    W = m*g*h = m*g*L*sin 30° = 4.8*9.80*2*0.5 = 47.0 joule

    (b)

    Determine the work W' done by the friction force between block and incline

    W' = m*g*cos 30°*μk *L = 4.80*9.80*0.866*0.436*2 = 35.5 joule

    (c)

    Determine the work W'' done by the normal force

    Normal force N = m*g*cos 30°

    W'' = N*h' ...h' being the displacement having the same direction of N

    since the block is in contact with the incline, then h' = 0 and W'' = 0 

    (d)

    How would the answers qualitatively  change if a shorter ramp at a steeper angle were used to span the same vertical height?

    # answer a) : W doesn't change , since h is the same 

    # answer b) : W' decreases, since both L and cos Θ are smaller 

    # answer c) : W'' still remains zero 

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