1. Define force. 2. Define pressure. …

1. Force is a push or a pull that changes or tends to change the state of rest or uniform motion of an object or changes the direction or shape of an object. It causes objects to accelerate. SI unit is Newton. 

2. The force acting on per unit area of a surface is called pressure. We can say force per unit area is called pressure.
                                                              Pressure = Force / Area

4. Muscular force:
(i) Force due to the action of muscles is called muscular force. We can say force resulting because of action of muscle is called muscular force.
(ii) Muscular force is applied only after interaction with the object.
Examples:
(a) When we push the object like school bag or lift the bucket of water we use the muscular force.
(b) Animals also use of muscular force to carry out their task.

5.  Gravitational Force:
(i) Gravitation force is exerted by earth, moon, sun and other planets to others.
(ii) Earth and other planets attract all objects towards them. Since, earth attracts all objects even without coming in contact, thus gravitational force is a non-contact force.
Example: When we release an object from a height, it falls over the ground because of gravitational                attraction of earth.

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