Net force?

Question

What net force is needed to maintain the constant velocity of a car moving in a straight line?

Answer 1

The answer is 0.

F = ma

for the vehicle to be at constant velocity you need acceleration (the change in velocity) to be zero. Thus the force equilibrium on the car is 0 to maintain the motion it already has.

Of course in the environment there's forces like friction, drag, and the fact that motors aren't 100% efficient - which is why you really need to invest energy (fuel) to keep a car moving.

Answer 2

depends on the environment.

in a vaccum, i.e. space... once the vehicle has acheived the desired velocity.. the net force would be zero.

newton's law of inertia.. 'an object at rest tends to stay at rest, an object in motion tends to stay in motion unless an external force acts upon it'.

in otherwords, in a vaccuum there are no other forces (i.e. friction/drag, gravity) acting on the car ...

in the case of a non vaccuum, then use newton's second law of motion

'the rate of change of the momentum of a body is directyl proportional to the net force ...'

so to keep a car moving in a constant straight line, calculate the net force of gravity + net force of drag (for this case, drag has more of an effect that gravity, assuming the road is perfectly level) call this net force FsubDrag, then apply that amount of for ce to the car, FsubTorque to keep it moving... all in all though the net force is zero since the car is not accelerating, slowing down,etc...


hope this helps...

good luck...

Answer 3

Well that depends on so many other factors, predominantly drag.