A 15,000lb freight car is pulled along a horizontal track. Ifthe car starts from rest and attains a velocity of 40ft/s aftertraveling a distance of 300ft. determine the total work done on the car by the towing forcein this distance if the rolling frictional force between the carand the track is 80lb. A 15,000lb freight car is pulled along a horizontal track. Ifthe car starts from rest and attains a velocity of 40ft/s aftertraveling a distance of 300ft. determine the total work done on the car by the towing forcein this distance if the rolling frictional force between the carand the track is 80lb.
Explanation / Answer
first find the acceleration with this equation:v22 = v12 + 2ad where v1 = 0, v2 = 40 ft/s, d = 300ft v22 = v12 +2ad a = (v22 -v12) / 2d =((40)2 - (0)2)/ 2(300) = 2.667 ft/s2 now use the equation Fnet = ma to find forceexerted Fnet is towing force minus the friction we will useF as towing force and Ff as friction Fnet = ma F - Ff = ma F - 80 = (15000)(2.667) F = (15000)(2.667)+ 80 =40080 lb now use equation W = Fd to find work done W = Fd = (40080)(300) = 12024000 J now use the equation Fnet = ma to find forceexerted Fnet is towing force minus the friction we will useF as towing force and Ff as friction Fnet = ma F - Ff = ma F - 80 = (15000)(2.667) F = (15000)(2.667)+ 80 =40080 lb now use equation W = Fd to find work done W = Fd = (40080)(300) = 12024000 J