# Force Required to Overcome Friction

## Main Question or Discussion Point

Hi,

My name is Michael Burt and I am level 3 physics student (high school), and I have a pretty general question about friction.

There's an old 2000 Toyota Corolla sitting in my backyard, and I was wondering what is the total forward force that the engine must create to move the vehicle, or even just the force threshold.

Some assumptions have to be made of course, involving rust and older parts. But I realize that the main friction is with the tires to the pavement, and moving parts within the vehicle.

The stock mass is listed at 1 095 kg, so I understand one of the forces of friction will be the normal force times the percentage of static friction...

Obviously there is a lot more going on here than just a normal force for friction, so maybe someone could explain to me other sources of friction with the vehicle!

I want to be able to find an electric motor to replace my gasoline engine (but maintain the same driveshaft, transmission and so on), using a variable power supply to act as throttle. And to my understanding, if I can calculate the forward force required to actually move the vehicle, then the wattage (J/s) of an appropriate motor could handle that.

Any advice/loop holes in my plan would be greatly appreciated,
Mike.

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jack action
Gold Member
See this http://hpwizard.com/car-performance.html" [Broken] for calculations and theory on the requirement for acceleration and speed for a vehicle.

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I'm not sure that's exactly what I'm looking for, but thanks.

It seems too simple that the force required to push the car in gear would be the same force required by the engine (or electric motor) to move it?

jack action
Gold Member
I'm not sure that's exactly what I'm looking for, but thanks.

It seems too simple that the force required to push the car in gear would be the same force required by the engine (or electric motor) to move it?
I'm not sure what you mean by «push the car in gear», but the fact is that when the car will be in motion, there will be an acceleration and a velocity (no matter how small they are). These will determine the inertia and drag force to be compensated in addition to the rolling resistance (again, no matter how small they are). From there, about 15-20% of the total force needed will be to fight internal friction and inertia of the rotating components (wheels, gears, crankshaft, etc.)

There is no other way around it.

How fast you want to go (acceleration and velocity) will determine how much power you need; even if you are pushing the car with your hands!