A sled with mass 8.00 kg moves in a straight line on a frictionless horizontal surface. At one point in its path, its speed is 4.00 m/s; after it has traveled 2.50 m beyond this point, its speed is 6.00 m/s. Use the work-energy theorem to find the force acting on the sled, assuming that this force is constant anti that it acts in the direction of the sled’s motion.

Solution 23E Step 1: As per the question, the mass of the sled, m = 8 kg Initial velocity of the sled, u = 4 m/s Final velocity of the sled, v = 6 m/s The distance travelled, S = 2.50 m According to the work- energy theorem, the change in kinetic energy = work done on the system That is, W = KE 2 2 KE = ½ mv - ½ mu KE = (½ × 8 kg × 6 m /s ) - (½ × 8 kg × 4 m /s ) 2 2 2 2 2 2 2 KE = ½ × 8 kg × (36 m /s - 16 m /s ) KE = ½ × 8 kg × 20 m /s = 80 J 2 2