10. Joe places two solid objects in contact with each other. Which property determines the direction of the flow of heat between the two objects?
A. Material of the objects.
B. Volume of the objects.
C. Density of the objects.
D. Temperature of the objects.

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.