Which of these is a good example of newton's first law of inertia

a) a ball sits motionless on the ground

b) a ball gathers speed as it rolls downhill

c) a ball accelerates as it falls out of the classroom window

d) a ball slows down after it is kicked through the grass

A1-lb collar is attached to a spring and slides without friction along a circular rod in a vertical plane. the spring has an undeformed length of 5 in. and a constant k =25 lb/ft. knowing that the collar is released from being held at a determine, the speed of the collar and the normal force between the collar and the rod as the collar passes through b.