Calculating Force Needed to Maintain Constant Speed in Car

[TT0]

A car whose mass is 1000 kg is traveling at a constant speed of 10ms^-1. Neglecting any friction, how much force will the engine have to supply to keep going the same speed?

F = ma

Since it is traveling at a constant speed then acceleration = 0 ms^-2 hence the answer is 0.
F = m x a
F = 1000 x 0
F = 0

My question is:
Firstly am I right?

And secondly why does everything have to be accelerating? If the car was traveling at a constant speed of 10ms^-1 and there was friction how would you calculate the force needed?

 

[mrnike992]

If the car is traveling in a straight line without going up hill or anything like that, then yes, the force is zero. If there was friction, the force would have to be equal to force friction, so that the ΣF=0.

 

[TT0]

Ok thanks

 

[haruspex]

If the car was traveling at a constant speed of 10ms^-1 and there was friction how would you calculate the force needed?

To be clear, friction between tyres and road only slows a car down when the car is braking. In the real world, a car traveling at constant speed on the flat needs power to overcome drag, axle friction and rolling resistance. Rolling resistance is the force required to deform the tyres as they rotate.

 

[jitti]

It"s right if you are in space no friction .

 

[mrnike992]

Uh, there is friction in space..

 

[mrnike992]

There's just a lot less air resistance or drag force

 

[ch2831]

If there is friction, and you want to keep the car traveling at constant speed, the force going forward would have to be equal to the retarding force of the friction (to balance it out). But yes, your answer is correct :)

 

[TT0]

Thanks everyone