A 15,000lb freight car is pulled along a horizontal track. Ifthe car starts from

Question

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

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