Force and Motion

Force:

Ø The pull or push of a body which changes or tends to change the position of the body is called Force.

·     Force is the main factor that brings changes on the position, motion, shape, size etc.

·     In every action there is a pair of force which can be balanced or unbalanced.

Balanced force

Ø When a number of force acting on a body do not change the state of rest or uniform motion then the force is said to be balanced.

Unbalanced force:

Ø When a number of force acting on a body change the state of rest or uniform motion then the force is said to be unbalanced.

Velocity:

Ø The displacement per unit time is called velocity.

Ø Its SI unit is m/s.

Ø It is a vector quantity.

Speed:

Ø The distance travelled per unit time is called Speed.

Ø Its SI unit is m/s.

Ø It is scalar quantity.

Uniform and non-uniform velocity:

Ø A body is said to be in uniform motion if it covers equal distance in an equal interval of time on a straight line.

Ø A body is said to move in non-uniform velocity if it covers unequal distance in equal intervals of time on a straight line.

Acceleration:

Ø The rate of change of velocity is called Acceleration.

Ø Its SI unit is m/s².

Retardation:

Ø Retardation is also known as negative acceleration.

Ø Its SI unit is m/s².

Inertia:

Ø The property of a body due to which it remains or tends to remain in the original state of rest or uniform motion on a straight line unless an external force acts on it is called inertia.

Forms of Inertia:

Inertia of rest:

Ø Inertia of rest is the property of a body by virtue of which it remains or tends to remain in the state of rest unless external force is applied.

Ø For example:

1.  When we stand or zit loosely on a bus and the bus suddenly starts to move, we jerk backwards on the bus.

2.  When a blanket is given a sudden jerk, the dust particles fall off.

Inertia of motion:

Ø Inertia of motion is the property of a body by the virtue by which it remains or tends to remain in the state of uniform motion unless external force is applied.

Ø For example:

1.  Passengers in moving bus jerks forwards when the bus stops suddenly.

2.  A coin thrown vertically upwards in a moving bus comes back in the hands of the thrower.

Inertia of direction:

Ø Inertia of direction is the property of a body by virtue by which it maintains or tends to maintain its direction unless external force is applied.

Ø For example:

1.  When a running bus suddenly takes a turn the passengers experience a jerk in the opposite direction.

2.  When the wheel rotates at a high speed, the mud sticking to the wheel flies out tangentially.

Newton's law of motion:

Newton's first law of motion:

Ø Newton's first law states that everybody continues to remain in its state of rest or uniform motion unless external for is applied.

Newton's second law of motion:

Ø Newton's second law states that's acceleration produced in a body is directly proportional to the force applied to it in the direction of motion and inversely proportional to its mass.

Newton's third law of motion:

Ø Newton's third law states that "to every action, there is an equal and opposite reaction."