A dog can provide sufficient power to pull a sled with a 60 N force at a steady 2.0 m/s. Suppose the dog is hitched to a different sled that requires 120 N to move at a constant speed. How fast can the dog pull this second sled?
Applying the definition of power (rate of change of energy with respect to time), and the definition of average speed, we can say that the power is the product of the net force applied, times the speed achieved by the force on the mass of the object, as follows:
P = F* v
In this case, this power can be written as follows:
P = 60 N * 2.0 m/s = 120 J/s = 120 W
If the power remains constant, but now it is required a force of 120 N to move the sled at a constant speed, it is clear that the maximum speed possible will be 1.0 m/s, due to 120 N* 1.0 m/s = 120 W, which is the maximum power available.
