A slide in a park possesses a total length of 10 ext m and a height of 8.0 ext m . A vertical ladder is provided to reach the top. A boy weighing 200 ext N ascends the ladder to the upper end of the slide, then slides down to the ground. The slide offers an average friction equal to three tenths of his weight. Find the work done by the ladder on the boy as he goes up. Neglect any work done by forces inside the body o

Step-by-step solution

Let the boy be considered as a point mass since the work done by internal forces is neglected. The boy starts from rest at the bottom and comes to rest at the top, so the change in his kinetic energy is zero, K = 0 . The external forces acting on the boy are the downward force of gravity and the upward force exerted by the ladder. The work done by gravity as the boy ascends a height h = 8.0 m is given by: W_ g = -mgh Since the boy's weight is mg = 200 N , the work done by gravity is: W_ g = -200 8.0 = -1600 J Apply