Answer:
Explanation:
At the top of the hill, the sledges possess a potential energy E equals to mgh. During the motion, this energy is converted into the work A1 in overcoming the force of friction along section DC and into the work A2 in overcoming the force of friction along section CB, i.e.,
E = mgh = A1 + A2.
Since l/S < 1, a1 > 0 and the sledges will move with uniform acceleration along section DC. The acceleration along section CB is a2 = — kg, and the sledges decelerate uniformly.