Consider the total work done on an object that has several forces acting on it.

Question

Consider the total work done on an object that has several forces acting on it. A tractor is hitched to a sled loaded with firewood and pulls the sled a distance of 20.0 m along level frozen ground. Let’s determine what actually happened to the work energy produced by the forces acting on the sled. The free-body diagram is shown in (Figure 1) . We find that the total work done on the sled by all the forces is 10.0 kJ, so the kinetic energy of the sled must increase by 10.0 kJ. The mass of the sled is m=(14,700N)/(9.80m/s2)=1500kg. Suppose the sled’s initial speed vi is 2.00 m/s. It's final speed is 4.16 m/s. It's constant acceleration is 0.333 m/s^2. If the tractor pulls horizontally and the friction force has a magnitude of 3700 N , what is the magnitude of the force the tractor must exert to make the sled move with constant speed?

Explanation / Answer

force of friction= 3700 N

let applied force=F

now since the speed is constant, so acceleration a=0

F- Ff= m a

F- 3700= m (0)

F= 3700

so applied force = 3700 N

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