A 5-kg mass is raised a distance of 4 m by a vertical force of 80 N. Find the wo

Question

A 5-kg mass is raised a distance of 4 m by a vertical force of 80 N. Find the work done by the force and the work done by the earth and the final kinetic energy of the mass if it was originally at rest. An 8-kg sled is initially at rest on a horizontal road The coefficient of kinetic friction between the sled and the road is 0.4. The sled is pulled a distance of 3 m by a horizontally applied force of 50 N. Find the work done by the applied force, Find the work done by friction, Find the change in the kinetic energy of the sled. Find the speed of the sled after it has traveled 3 m. A 4-kg object is lifted by a rope exerting a force T so that it accelerates upward at 6 m/s2. The object is lifted 3 m Find the tension T, the work done by T, the work done by

Explanation / Answer

(a) W = F*d = 50*3 = 150 Nm

(b) f = mg

W = f*d = mgd = 0.4*8*9.8*3 = 94.08 Nm

(c) change in kinetic energy = 150 - 94.08 = 55.92

(d) 1/2 mv2 = Fd - fd

v = sqrt(2*(F-f)d/m)

= sqrt(2*(50 - 0.4*8*9.8)*3 / 8) = 3.74 m/s

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