Hourglass
Placing a dented table tennis ball in boiling water causes the air inside the ball to expand, pushing out the dent and restoring the ball's shape. The heat softens the plastic material of the ball, allowing it to return to its original state. Once the ball cools down, it retains its new shape.
The air inside expands when heated, and increases the interior pressure. Unless a ball is so badly crushed that it cannot become round again, the dented part will be pushed out to create its original shape.
Placing a dented tennis ball in boiling water causes the air inside to expand, pushing out against the dent and restoring its shape. The heat softens the rubber on the ball, making it more malleable and allowing it to regain its original form when the pressure is released.
The hot water causes the air trapped inside the ball to expand and it may pop the dent out to the original shape.
Weigh it down some how in water and boil the water,or you may also use the butt of a racket and round the ball back up
Metal when it gets hit, stays dented and looks terrible. Plastic either breaks or bounces back to original shape, thus defeating vandals' efforts. Plastics are probably cheaper to produ
a sphere
there is air inside a tennis ball. when it is hot, the air inside the ball is hot, and thus is excited. when the gas is excited it bounces around more inside the ball and causes it to be harder. when it is colder the gas is less excited so the ball feels softer. When you bounce a tennis ball on a hot day the ball is harder feeling and is essentially more elastic. this causes the ball to bounce higher. when it is colder the ball is less elastic and will not bounce up very high at all. think about the moment the ball hits the ground. if you threw it super hard the ball would momentarily get dented in. now if its hot the gas is excited and moving around a lot so it will push the dented in ball back out to its original shape very fast, where as if it is cold it will not push it back out as fast or hard so it will not bounce as high.
Cylinder
The name for the force exerted by a stretched or compressed elastic material is called "elastic force." It is the force that tries to restore the material to its original shape or size when it is deformed.
Similarity potential energy refers to the energy stored in an object when deformed from its original shape due to applied force, with the potential to restore back to its original shape once the force is removed. Elasticity refers to the ability of a material to return to its original shape after being deformed under stress, in the absence of any external forces.