Inertial Reference Frames

Soaring Crane

1) Which object provides an inertial frame of reference?

a. the tip of the moving second hand of a clock
b. a rock thrown vertically upward
c. a pendulum swinging with no air resistance
d. a skydiver falling at terminal velocity

At first I thought c might be correct, but now I am confused. The earth is a reference frame?

2) You are conducting an experiment inside an elevator that can move in a vertical shaft. A load is hung vertically from the ceiling on a string. The tension in the string is measured to be 10% less than the weight of the load. No other forces are acting on the load. Which of the following statements about the elevator are correct? (> 1 can be correct)

A.The elevator is an inertial frame of reference.
B.The elevator is not an inertial frame of reference.
C.The elevator may be at rest.
D.The elevator may be moving at a constant velocity upward.
E.The elevator may be moving at a constant velocity downward.
F.The elevator must be accelerating.

I think A, C, D, E may be correct, but I am not sure.

Thanks.

Physics is Phun

an inertial frame of reference is anything not accelerating.
I don't have time for # 2. sorry.