Consider a situation in which a ball is rolling on the ground. We observe that the ball finally stop after covering a certain distance.It will cover longer distance if the ground is made smoother.We can well assume that when the ground is perfectly smooth, the ball would continue moving forever in the same direction with a constant speed.It is the roughness of the surface that provides opposing force called friction,to stop the ball from moving.Thus,to bring a body into rest from the state of motion,force has to act on it in opposite direction of its motion.
Consider a very big stone at rest to which boy cannot move by pushing or pulling it.This means, the force exerted by the boy is insufficient to move the stone.Similarly, a moving body cannot be stopped if the applied force is insufficient.Only sufficient force can do this.A body having a small mass requires less force to move or to stop.
Thus, 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 acting on a body can do the following things:
1.It can change the speed of the body.
2.It can change the direction of motion of body.
3.It can change the shape and size of the body.
4.I t can change the position of the body.
The SI unit of force is newton(N).In CGS system,the unit of force is dyne.
1 Newton=100000 dynes.
Force is measured bu using a spring balance or a top pan balance.
Balanced and unbalanced forces
When a number of forces acting on a body do not change its state of rest or uniform motion in a straight line,the forces are said to be balanced forces.For example, in the game of tug of war,two teams pull a rope in opposite directions.When the two teams exert equal and opposite forces on the rope,the rope remains steady and does not move in any direction.It appears as if no force is acting on the rope.Thus, the two forces acting on the rope in this case are balanced forces.
When a number of forces acting on a body change its state of rest or uniform motion in a straight line,the forces are said to be unbalanced forces.For example,if we push a toy car towards east,it moves towards east.If it is pushed towards west,it moves towards west.This unbalanced force produces motion.
Inertia
The property of a body due to which it remains or tends to remain in the state of rest or uniform motion in a straight line unless an unbalanced force act on it, is called inertia.Only unbalanced force can change the state of rest of the state of motion and vice versa.Because of this property of the body,it opposes any change in its state of rest or of uniform motion in a straight line.
Consider a very big stone at rest to which boy cannot move by pushing or pulling it.This means, the force exerted by the boy is insufficient to move the stone.Similarly, a moving body cannot be stopped if the applied force is insufficient.Only sufficient force can do this.A body having a small mass requires less force to move or to stop.
Thus, 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 acting on a body can do the following things:
1.It can change the speed of the body.
2.It can change the direction of motion of body.
3.It can change the shape and size of the body.
4.I t can change the position of the body.
The SI unit of force is newton(N).In CGS system,the unit of force is dyne.
1 Newton=100000 dynes.
Force is measured bu using a spring balance or a top pan balance.
Balanced and unbalanced forces
When a number of forces acting on a body do not change its state of rest or uniform motion in a straight line,the forces are said to be balanced forces.For example, in the game of tug of war,two teams pull a rope in opposite directions.When the two teams exert equal and opposite forces on the rope,the rope remains steady and does not move in any direction.It appears as if no force is acting on the rope.Thus, the two forces acting on the rope in this case are balanced forces.
When a number of forces acting on a body change its state of rest or uniform motion in a straight line,the forces are said to be unbalanced forces.For example,if we push a toy car towards east,it moves towards east.If it is pushed towards west,it moves towards west.This unbalanced force produces motion.
Inertia
The property of a body due to which it remains or tends to remain in the state of rest or uniform motion in a straight line unless an unbalanced force act on it, is called inertia.Only unbalanced force can change the state of rest of the state of motion and vice versa.Because of this property of the body,it opposes any change in its state of rest or of uniform motion in a straight line.
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