A truck runs into a pile of sand moving 080 m as it slows to

A truck runs into a pile of sand, moving 0.80 m as it slows to a stop. The magnitude of the work that the sand does on the truck is 6.0 times 10^5 J. (a) Determine the average force that the sand exerts on the truck. (b) Did the sand do positive or negative work? (c) How does the average force change if the stopping distance is doubled? Indicate any assumptions you made.

Solution

The average force is F = W/s = 4.8x10^5 N

Work done by sand is negative because it opposes the motion of the truck

Average force is inversely proportional to displacement so the force is halved when the distance is doubled

That is

F_new=F/2=2.4×10^5 N