Assume that the reference frame is moving with the person indicated in each of the following situations. In which case is the reference frame noninertial?
a. The person is walking at a constant speed along a straight, horizontal sidewalk.
b. The person is walking at a constant speed along a straight sidewalk that is inclined downward at a slight unchanging angle.
c. The person is riding an elevator upward at constant speed. d. The person is skydiving and is freefalling not yet having opened her parachute.
Question 2
In order to train for a high-g environment, an astronaut is placed in a centrifuge of radius several meters and rotated in a horizontal circle at constant speed. In this situation, in which direction is the net force on the astronaut?
a. The net force is down since gravity cannot be turned off.
b. The net force is horizontal toward the center of the circle.
c. The net force is between horizontal toward the center of the circle and straight up, the angle depending on the speed and the radius involved. d. The net force is zero since the astronaut is moving at constant speed and thus the force has no direction.
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