Class 8 Physics Force and Pressure Contact forces and Non-contact forces

Contact forces : Force that arises with the contact of 2 or more objects involved. Examples : Muscular force and Frictional Force

Muscular force is the type of force wherein we use our physical strength to change the state of motion of an object. Eg: Man pushing a car, Bullocks pulling a cart of load, Cycling, Weight Lifting

Frictional Force is a force that acts on all moving objects by the surface which it is in contact with. Eg: A ball rolling on the ground encounters friction by the ground surface and it eventually comes to a halt. When the rowing of the boat has stopped, the boat comes to a stop because of the frictional force exerted by water on it. The Frictional force is always in the direction opposite to the applied force.

Non-contact forces: Forces that arise without the contact of 2 or more objects involved. Examples: Magnetic Force, Electrostatic Force, Gravitational force.

Magnetic Force is a force that attracts certain metal objects (like iron and iron filings) towards a magnet.

Electrostatic force is the force exerted by a charged body on another charged or uncharged body. Eg: Take a comb and brush it on a hair 3-4 times and then take it near some small bits of paper. Donot touch the comb with the paper. The bits of paper would get attracted to the comb. This is because the comb is charged because of the rubbing on your hair and it attracts uncharged objects like paper.

Gravitational force is a force exerted by the earth on all objects on it. When a ball is thrown up, it falls to the ground because of gravitational force. The water from a tap always flows downwards because of gravitational force.

.