The excretory materials are carbon dioxide, nitrogenous wastes, excess salts, and excess water, They are the waste materials which produced inside the cells and the body must get rid of them.
When we eat, some food is digested, then the blood carries the digested food to all the body cells, The cells consume the digested food to produce energy and release some useless materials into...
When any object moves through the water (such as the fish, the swimmer, the dolphin, and the ship), there is a friction force arises between this object and the water which is called water...
When a solid object moves in the air, a friction force arises between the object and the air, This type of friction is called the air resistance and it acts in the opposite direction...
