Rubber balls bounce due to the release of pressure from rubber’s molecules. When rubber meets a stationary object, it builds compressed energy and releases upwards to regain form.
Rubber is a strong material that withstands deformation. Rubber can be stretched, squeezed and dropped from dizzying heights without taking on physical damage. The material’s strength and elasticity are the key characteristics that cause rubber balls to bounce.
Rubber’s elastic material is the primary reason why rubber balls bounce. Elasticity is the tendency for objects to retain their original shape. When dropping a rubber ball, the part of the ball that hits the ground flattens out. Rubber’s elastic nature causes the ball to reactively return to its round shape, which pushes the ball upwards, causing it to bounce.
Rubber’s molecular structure is responsible for the bouncing ball as well. Rubber is a polymer, and like all polymers, it has relatively long and aligned molecules. These lengthy and linear polymeric chains are also a main contributor to bouncing.
Cross-linking is another characteristic that helps rubber balls bounce. The molecular chains that comprise rubber are linked to other molecular chains. Much like elasticity, if these chains were not bound, rubber balls wouldn't be able to bounce because they would fail to return to their original or spherical shape.