Question

A. Imagine a car (1000 kg), that feels horizontal forces: a drag force, a forward-pointing rolling friction force (frF)on two of its tires, and a backward-pointing rolling friction force (fre) on its other two tires. The car is speeding up. The car is moving to the left. Therefore, I choose to make left the positive direction. Here is a free-body diagram (not quite complete) that shows all the forces acting on the car. To be a complete free-body diagram, there needs to be an arrow representing the net force. This net force arrow would point to the (right, left] ty NH -y FD fRF fRB w 1. The y-component of the car's velocity is [increasing, decreasing, constant]. 2. Therefore, the y-component of the car's acceleration is (positive, negative zero). 3. Therefore, the y-component of the net force on the car is (positive, negative, zero] 4. Your answer to part 3 tells us that N[>,5, < W. 5. Write the algebraic expression that shows how the horizontal forces combine to produce the net force, just as I did in the examples in the video. Write it in the form “Fner = the algebraic expression." Be sure that each force appears in the expression with the correct sign.

Answer 1

1)

The y - component of car's velocity is constant. There is no force in y - direction which affects the car's motion.

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2)

The y - component of car's acceleration is zero.

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3)

As acceleration is zero in y - direction, net force is also zero.

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4)

Fnet = 0

N - W = 0

N = W

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5)

Left is positive

so,

Fnet = f_RF - f_RB - F_D