5. While a car travels around a circular track at constant speed its

A) acceleration is zero.

B) velocity is zero.

C) both of these.

D) neither of these.

[[[Picked D]]]

6. An airplane whose airspeed is 200 km/h is flying in a wind of 80 km/h. The airplane's speed relative to the ground is between ___________________.

A) 80 and 200 km/h

B) 80 and 280 km/h

C) 120 and 200 km/h

D) 120 and 280 km/h

[[[Picked D]]]

7. A bicycle and its rider together have a mass of 80 kg. If the bicycle's speed is 6 m/s, the force needed to bring it to a stop in 4 s is ___________________.

A) 12 N

B) 53 N

C) 120 N

D) 1176 N

[[[Picked C]]]

8. Which is heavier: 50 Lbs or 50 N?

A) 50 Lbs is heavier.

B) 50 N is heavier.

C) They are the same weight.

[[[Picked A]]]