What will the motion of the cart be like when there is no force at all ? ( there is no friction in this model. )

Explanation:

the cart motion will be backward motion for there is no action force generated via friction force which acts on the ground harness of the horse. thus the will be pulled backward by the cart.

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.