Look at the rock sitting on the hill in the picture above. Gravity should make the rock slide down the hill. What force is acting to balance gravity, keeping the rock in place?
A. centripetal force
B. gravity
C. momentum
D. friction

Question

Look at the rock sitting on the hill in the picture above. Gravity should make the rock slide down the hill. What force is acting to balance gravity, keeping the rock in place?
	A.  	centripetal force
	B.  	gravity
	C.  	momentum
	D.  	friction

anonymous · Answer

An object's motion changes
	A.  	when the forces acting on the object remain balanced.

	B.  	only if the object is at rest when a force acts upon it.

	C.  	only when a nonzero net force is applied to the object.

	D.  	all of these

anonymous · Answer

Could someone please help me?

mstoldegon · Answer

Very briefly, D for your first question (I can't see the picture but the others are not likely), C for the second.