A 5.3-kg block is pushed 3.4 m up a vertical wall with constant speed by a const

Question

A 5.3-kg block is pushed 3.4 m up a vertical wall with constant speed by a constant force of magnitude F applied at an angle of theta = 30 degree with the horizontal, as shown in the figure below. If the coefficient of kinetic friction between block and wall is 0.30, determine the following. (a) the work done by F 375.4 (b) The works done by the force of gravity -180.2 (c) The work done by the normal force between block and wall 0 J (d) By how much does the gravitational potential energy increase during the block's motion? 151

Explanation / Answer

(a)

along vertical

F*sintheta - mg = 0

F*sin30 - (5.3*9.8) = 0

F = 103.88 N

work done by F

WF = F*y*sintheta

WF = 103.88*3.4*cos60

WF = 176.6 J <<<--------answer

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(b)

Wg = -m*g*y = -5.3*9.8*3.4 = -176.6 J <<<--------answer

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(c)

Work done by normal force Wn = N*y*cos90 = 0 J

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(d)

increae in gravitationalpotential energy -Wg = 176.6 J <<-----answer

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