Free Body Diagram -- Force on a Car (Quick Question)?

Question

I need some quick help to a physics problem.

1) A car is moving at a constant velocity to the right

There is the force of air resistance and the force of the road on the car. (as well as gravity and normal force).

My question is...would the force air and force road be equal because the velocity is constant?


2) If the car is speeding up would the force from the road be greater or less than the force of air resistance?

(it doesn't mention friction in this problem but I'm assuming that's factored into the force of the road pushing back on the car and the spinning of the tires, engine etc)

And then if it's slowing down, same question-- which force would be greater: the force of the road or the force due to air resistance?


Thanks so much to all who answer!
I will be sure to choose a Best Answer!

the force of the air resistance is pulling towards the left (behind the car) in the free body diagram


and the force of the road is pulling out in front of the car to the right in the free body diagram

Answer 1

1) According to your FBD, you are correct, the magnitudes are equal.

2) since F=m*a, and there is a positive a, then the net force of the road is greater than air resistance.

BTW: The frictional forces are in the air resistance or netted out of the force of the road.

j

Answer 2

1/ As long as it's on the level ( so that the normal and gravity exactly cancel each other )

2/ again if its on the flat greater

slowing down - hard to tell , if it's slowing down really quickly then the road force could be much greater than the air resistance (they're both acting in the same direction by then as you are braking).

Answer 3

one million) Its weight as a result of the presence of its mass in an acceleration subject (ie Newtons second Law of movement, Force = mass x acceleration. the mass this is 40kg and the acceleration is nine.81m/s/s toward the earth. two)Being on a horizontal floor and obeying Newtons third Law of movement - to each movement there's a response in essence - and hence assuming no vertical airplane movement, there can be an same and reverse directional drive to that mentioned in (one million) exerted on the factor of touch among the item and the skin. three) The horizontal drive being implemented to the field (ie 200N). Easy huh? four) The frictional drive will act on the field / floor interface and within the reverse course to the boxs' horizontal movement - through definition. Note in view that the field has been mentioned to be relocating, that is kinetic friction and no longer static friction. Don't confuse the 2 in view that static can in a few instances be bigger in significance than kinetic, until it breaks down and turns into kinetic friction because the implemented drive is expanded past its static threshold.