you and your friend peter are putting new shingles on a roof pitched at 25. you
ID: 1762264 • Letter: Y
Question
you and your friend peter are putting new shingles on a roof pitched at 25. you are sitting on the very top of the roof when peter, who is at the edge of the roof directly below you, 5.0 m away, asks you for the box of nails. rather than carry the 2.5 kg 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 kinematic 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?Explanation / Answer
The force acting on the nail box in the x and y directionsare Fx = w2 - fk = w *sin - k * n ----------(1) and Fy = n + (-w1) = n + (-w *cos) = 0 or n = w * cos -----------(2) From equations (1) and (2) we get Fx = w * sin - k * w *cos or m * ax = w * (sin - k *cos) = mg * (sin - k *cos) or ax = g * (sin - k *cos) we know that v2 - u2 = 2ax * S where v = 0 and S = 5.0 m or 02 - u2 = 2 * g * (sin -k * cos) * 5.0 or u = -[10 * g * (sin - k *cos)]1/2 g = 9.8 m/s2 or u = -[10 * 9.8 * (sin - k *cos)]1/2 or u = -9.8 * (sin - k *cos)1/2 k = 0.55 or u = -9.8 * (sin - 0.55 *cos)1/2 The negative value of velocity indicates that the force offriction opposes the motion of the box of nails. The negative value of velocity indicates that the force offriction opposes the motion of the box of nails.Related Questions
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