Let consider, a object or a book lying on the desk. It does not move or continuous to b
e lying on that desk forever at the same position until somebody displace it to the other places or position. For moving that book somebody have to either pull and push it. Then such pull and push on a body or a object is called Force. Therefore it is clear that force is must be applied to body to bring the body into motion to rest and rest to motion. Similarly, "Force is an agent which tries to change the body condition from motion to rest or rest to motion." Let assume that the ball is rolling on the rough ground . We can see that the ball stops after covering the certain distance. It takes longer and longer time to stop on the smooth ground as that rough ground. So, we can well assume that when the ground is perfectly smooth then the ball would continue moving forever in the same direction with a constant speed. It is the roughness of the surface which provides opposing force called Friction, which tries to stop the ball from moving. So to bring a body into rest to motion, force has to act on it in opposite direction of its motion. In the another word, Force is that push or pull on a body that changes or tends to change the state of rest or of uniform motion in a straight line.
Force action on a body can do the following things
1. It can change the shape of the body .
2. It can change the speed of the body.
3. It can change the direction of motion of the body.
Balanced and UnBalanced Forces
When the forces are given to as body if the body do not change its state of rest or of
motion states then the given forces are called Balanced Force. For example ; If two persons are pulling the rope in opposite forces then the rope does-not move in any side and the rope remains steady. Thus, the two forces act by the persons on the rope are Balanced Forces in this case.When the forces are given to as body if the body changes its state of rest or of motion states then the given forces are called Unbalanced Force. For example ; If a person pulls the object towards the west then the object also moves towards the west. If again it pulled towards the North then it moves towards the North. Then, this force act on object are Unbalanced forces in this case. This unbalanced forces produces motion.
Inertia
Inertia is the property of a body due to which it remains to remains in state of motion or of rest in a straight line without unbalanced force can only change the state of rest to motion and vice-versa because it opposes any change in its state of rest or of uniform motion in a straight line.
Inertia may show itself as the following three forms:
1. Inertia of Rest
2. Inertia of Motion
3. Inertia of Direction
1. Inertia of Rest
It is the property of a body by virtue of which it remains to be still n state of rest until the unbalance force is act on the body.
Example:
a) When we are standing in the bus if the bus suddenly starts then we fall backwards because at first our whole body is in rest. When the bus suddenly starts then our lower part of the bus comes to motion but the upper part remains in rest due to inertia of rest.
b) When we hit the blanket then the dust particles falls down. This is because at first both dust particles and the blankets are in rest position. When we hit the blankets then it comes into motion but the particles remains rest due to inertia.
2. Inertia of Motion
It is the property of a body by virtue of which it remains to be still in the same as in motion unless unbalanced force are act on in it.
Example:
a) We are standing in a moving bus. When it suddenly stops then we falls forward. This is because at first both parts of our body are in motion. When bus suddenly stops then our lower part comes in rest but upper part remains in motion due to inertia of motion.
b) An athletic runs for some distance before taking a long jump. Because by running for some distance he/she gains more inertia of motion which helps him/her to take a long jump.
3. Inertia of Direction
It is the property of a body by virtue of which maintains to maintain its direction of motion until unbalanced forces are act on it.
Example:
a) When a moving bus suddenly takes turns then the people sitting in the bus, they experience a jerk in the outward direction. This is because the people tend to maintain their original direction of motion due to inertia of direction.
b) When the wheel rotates at a high speed then the mud which is sticking at the wheel files off tangentially. This is due to inertia of direction.
VECTOR
Those quantities which have both magnitude and direction are called vectors. Some examples of vector are Velocity, Acceleration, Force, Displacement, etc. The sum of vectors may be zero, position and negative. They are added by certain vector rules. Vector is simply represented by letter 'A' or by letter bold letter P.
SCALARS
Those quantities which have only magnitude but not direction are called scalars. Some examples of scalars are Distance, Speed, Work, etc. The sum of Scalar are always position number. they are added by the simple rules and it is simply represented by letter 'a' and P.
DISTANCE
The actual path or length which traveled by the body is known as distance. It is scalar quantity. Its S.I. unit is meter (m). A body should covered between initial and final position. The net distance covered cannot be zero.
DISPLACEMENT
The shortest distance which is between the initial position and final position is known as displacement. It is a vector quantity. It is also measured in S.I. system in meter (m). The net displacement may be zero.
SPEED
The distance traveled per unit time is known as speed. It is a scalar quantity. It is always positive. It is represented by V letter. Its S.I. unit is measured in m/s.
VELOCITY
It is defined as the distance covered by a body per unit time. Its S.I. unit is m/s. It is vector quantity because it has both magnitude and direction and can be positive and negative.
