Thursday, May 17, 2007

X-revision Force

What is a force?

A force is that physical cause which changes or tends to change the state of rest or the state of motion of a body.

Newton’s laws of motion

First law – a body continues to be in its state of rest or of uniform motion in a straight line, unless an external force is applied on it.

Second law - the rate of change of momentum of a body is directly proportional to the force applied on it and this change takes place in the direction of force.

Third law – to every action, there is always an equal and opposite reaction.

What is linear momentum?
The linear momentum of a body is the product of the mass of the body and its linear velocity. It is a vector quantity

One dyne is that force which when acting on a body of mass 1 gramme, produces an acceleration of 1 cm s^-2(to the power of -2) in it.

One Newton is that force which when acting on a body of mass 1 kg, produces an acceleration of 1 m s^-2 in it.

The Newton and dyne are called the absolute units of force.

What is mass?
The mass of a body is the quantity of matter it contains.

The S.I. Unit of mass is kilogramme (kg).
The C.G.S. unit of mass is gramme (g).

What is weight of a body?
The force with which the earth attracts a body, is called the weight of the body on earth.