Answer :
Since no external force is acting except frictional force, so stopping force is frictional force with magnitude ~ 3N in the direction opposite to the motion of sledge.

A sled is pushed along an ice-covered lake. It has some initial velocity before coming to rest in 15m. It took 23 seconds before the sled and rider came to a rest. If the rider and sled have a combined mass of 52.5 kg, the magnitude, and direction of the force - 2.98 N which is called friction.
Given:
Time t = 15 s
distance d = 23 m
mass = 52.5
As we know the formula,
[tex]Solution:\\\\\\bar v = \frac{d}{t}\\\\ = \frac{15}{23}\\ \\ = 0.65 \ m/s\\\\According\ to\ the\ question,\\v_f =0\\then,\\2 \bar v = v_i\\2(0.65)=v_i\\v_i=1.3 \ m/s\\u = Initial\ velocity,\\v = Final\ Velocity,\\a = acceleration\\\\According\ to\ the\ second\ law\ of\ motion\\Force = m\times a\\ = (-.057)\times 52.5\\ = -2.97 \ N[/tex]
Thus, F is taken to be negative. So, the stopping force is -2.97 N and this force is the frictional force and its direction is opposite to that of motion.
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