Posted by Sandy on .
4. An ice skater pulls three small children, one behind the other, with masses 25kg, 31 kg and 35kg. Assume that the ice is smooth enough to be considered frictionless, determine:
a) the total force applied to the train of children if they reach a speed of 3.5m/s from rest in 15 s;
b) if the skater is holding onto the 25kg child, find the tension in the arms of the next child (31 kg) in line.

physics 
Henry,
a. a = (3.5  0) /(15  0)=0.23m/s^2.
F = ma = (25 + 31 + 35) * 0.233,
= 91 * 0.233 = 21.2N.