Question

A SUV manufacturer puts out 2 models of SUV - both with the same body shape (use the streamlined truck C_D of 0.55 if necessary) and the same quality of wheels and bearings, but model B (for "Bigger") is twice as big as model A - twice as wide, twice as tall, twice as long, and 8 times as heavy. At the same speed, the force of aerodynamic drag on model B will be:

B) 8 times larger than on model A

C) the same as on model A

D) 4 times smaller than on model A

E) 4 times larger than on model A

F) 8 times smaller than on model A

1. Keeping with the premise of the previous problem: At the same speed, the rolling resistance force on model B is
   approximately:
   
   B) 4 times smaller than on model A
   C) 8 times larger than on model A
   D) the same as on model A
   E) 4 times larger than on model A
   F) 8 times smaller than on model A

1. Keeping with the premise of the previous 2 problems: At the same speed and on a hill of the same grade, the
   hill-climbing force on model B is:
   
   A) 8 times smaller than on model A
   B) 4 times smaller than on model A
   C) 8 times larger than on model A
   E) the same as on model A
   F) 4 times larger than on model A

1. Keeping with the premise of the previous 3 problems: Going up the same hill, the engine of model A provides
   enough acceleration force to keep it moving at a constant velocity. If the engine of model B provided the same
   acceleration force, model B would be:
   
   A) moving with a different constant velocity
   B) decelerating
   C) accelerating
   E) coming to an immediate stop
   F) moving with the same constant velocity

Answer 1

1) The aerodynamic drag is proportional to the area of the front surface of the vehicle.

Here, the width and the height of the vehicle B is twice as that of A

So, the area will be 4 times larger.

and the drag will also be 4 times larger.

Option E is correct.

2) The rolling friction is proportional to the mass of the vehicle.

Mass of B = 8 times mass of A (larger).

So, rolling friction = 8 times larger than that of A

Option C is correct.

3) The air drag is dominant compared to rolling friction for a car.

So, the drag force is 4 times for car B

The applied force must also be 4 times , so that a hill can be climbed.

Option F is correct.

4) As in C, engine B must provide 4 times more force to travel at the same velocity.

Since the force is same, the car B will be decelerating.

Option B is correct.