Question

1.) Why do some objects fall faster than others near the surface of the earth if all mass is attracted equally by the force of gravity?

A. Some objects fall faster because of air resistance, which acts in the direction of the motion of the object and exerts more force on objects with less surface area.

B. Some objects fall faster because of air resistance, which acts in the direction opposite the motion of the object and exerts more force on objects with less surface area.

C. Some objects fall faster because of air resistance, which acts in the direction of motion of the object and exerts more force on objects with more surface area.

D. Some objects fall faster because of air resistance, which acts in the direction opposite the motion of the object and exerts more force on objects with more surface area.

2.) A 50 kg bicyclist starts his ride down the road with an acceleration of 1m/s2 in air with a density of 1.2 kg/m3. If his velocity at a given moment is 2m/s, how much force is he exerting? Assume the area of his body is 0.5m^2.

A. The bicyclist is exerting 1.1 N of force

B. The bicyclist is exerting 49 N of force

C. The bicyclist is exerting 50 N of force.

D. The bicyclist is exerting 51 N of force

3.)Calculate the angular speed of a 0.2m radius car tire when the car travels at 10⁣m/s.

A. 0.02 rad/s B. 2 rad/s C. 5 rad/s D. 50 rad/s

4.) Recent studies have shown that spending time at a lower temperature can help increase weight loss through thermal uncoupling and shivering. Assuming a person spends 2hr per day for a week in temperatures cold enough to induce shivering, how much additional energy are they using? What can you infer about the effectiveness of this weight loss technique?

A. 21.4 x 10³ kJ - this would NOT be an effective weight loss method.

B. 21.4 x 10³ kJ - this would be an effective weight loss method.

C. 5950 kJ - this would NOT be an effective weight loss method.

D. 5950 kJ - this would be an effective weight loss method.

Answer 1

1 Answer D - The air resistance acts in a direction opposing the motion. The resistance increses as surface area of the body presented to air is more.

2. The cyclist has to exert some extra force to over come air resistance. Now, he requires to exert a foce of 50Kg x 1m/s^2 = 50 N , if there were no air resistance. So with air resistance he has to extert force higher than 50 N and hence the answer is 51N

3. Answer D -

4. in option B , very high enrgy is burnt by the body -which is 21400 KJ-this is much higher that 5950 KJ- thus per day about 3000KJ energy is lost, which is good way to lose weight.