Question

Two children, m1 = 50 kg and m2 = 55 kg, and a plastic sled of mass 35 kg start at rest and slide for 5.0 s down a hill. The force of gravity pulling the children and sled down the hill is 470 N but the snow provides a frictional force of 325 N. At the bottom of the hill, the children and sled encounter a frozen pond (frictionless surface). Upon sliding onto the frozen pond, the children and sled continue moving, without any additional force, across the middle to the other side.

If the pond has a circumference of 163 m, to the nearest tenth of a second, how long did it take the children and sled to travel to the other side of the pond?