What is friction times velocity?

Question

A car is moving on a straght road with velocity v, the total opposing force is f, what is the product of f times v

Answer 1

As one answer put it "power." But I think you would appreciate a wee bit more...like the relationships among force, work, energy, and power.

Force is good old f = ma or f = kmg in the case of friction; where k is the friction coefficient and mg is the normal weight of a body of m mass.

Now work can be found from W = fd; where f is that force above and d is some distance the body m is moved by the force applied to it in the same direction as d.

Turns out that work is just another name for energy. But work is a more specific case where energy is expended through displacing something a distance d. Energy is a more generalized term that includes work and also chemical, electrical, thermal, nuclear, and other energy sources.

Finally, power is simply energy available or used over a specific period of time (t). For example if W = fd = kmgd, the work against friction, the power expended = P = W/t = fd/t =fv; where d/t distance over time is defined as velocity (v). And there you are...we have just derived why fv is power, and, in the meanwhile, we now know how power relates to force, work, and energy.

Answer 2

The opposing force (wind resistance, tire rolling resistance, friction between axle bearings etc) is the force that must be supplied to move the car forward. Who supplies it ? The road !
The tires kick back on the road, and the road in turn pushes the car. So, friction force that is required is same as the total opposing force .

Therefore F X V is the power that must be available to the axles.

Answer 3

Since the car is travelling at a constant velocity then there is no resultant accelerating force. This means that the force of the engine is equal to the total friction.

force x velocity = power

So here it would be the power produced by the engine.

This site will explain in further detail... http://www.glenbrook.k12.il.us/gbssci/phys/class/energy/u5l1e.html

Answer 4

E = Fd; Divide both sides by t (E=Energy; F=Force; d=displacement)

E/t = F d/t ; E/t = P d/t = v

Therefore

P = Fv

The answer is mechanical power of the car