How to Calculate Acceleration and Force in a Car

[cheerspens]

Homework Statement

a) A 3100 kg car can accelerate with a maximum acceleration of 3.0 m/s².
How long will it take this car to go from a velocity of 20 m/s to 40 m/s?

b) If there is a 4000 N force do to air friction opposing the car's motion, what is the strength of the force responsible for the car's acceleration?

c) What object exerts the force that accelerates the car?

Homework Equations

F_NET=ma
x=x_o+v_ot+.5at²
v=v_o+at

The Attempt at a Solution

a) I got an answer of 6.67sec.

b) I got an answer of 9700 N.

c) The tires? Because of friction?

 

[rock.freak667]

What causes the car to move in the first place is what I think they are asking for part c.

 

[cheerspens]

The road?

 

[rock.freak667]

The road?

Or it could be the engine causing the tires to rotate.