take a solid cylinder and a solid sphere both with same radii and mass. if you let them roll down an incline from the same position, which one will reach the bottom last?

Wooden , walls ,doors ,support

In the conservation of mass, mass (which is the same as energy) can never be created or destroyed in the same way oil is formed from the remains of small animals and plants that died and fell to the bottom of the sea and their mass (energy) is conserved as oil.