Force
Any push or pull acting on an object is called a force. The unit of force is Newton (N).
A force can
- Move a stationary object
- Stop a moving object
- Make a moving object move faster
- Slowdown a moving object
- Change the direction of a moving object
- Change the shape and size of an object
In the above examples, you can see that the force is being used to do something. Hence, force is an interaction between two objects. This interaction may be physical or non-physical. In a physical interaction, the objects come into contact and it is called a contact force. In a non-physical interaction, there is no contact and it is called action at a distance force.
Different types of forces
There are many forces acting on us. Some of them are:
Gravity: Gravitational force is the force that attracts one object to another. The bigger the mass, more is the pull of gravity. That is why the gravity of the earth is more than that of the moon as Earth is bigger than the moon. Gravity is also the reason why the solar system is in its place and why the planets go round the sun.
Balanced forces: Balanced forces are two forces that cancel out each other. For example, look at the boat floating on the water. The pull of the gravity is cancelled by the push of the water. As both the forces acting on the boat are equal, the boat stays afloat
Unbalanced forces:When the forces acting on an object are not equal, one force is bigger than the other. Then the object will move in the direction in which the bigger force wants it to move.
Friction: This force stops any object from moving. When an object moves on another object there is friction at the point of action. The rougher the surface of the object, the higher is the friction. Friction acts against the direction of the movement and slows down the object. It is easier for us to slide down snow than it is to on gravel. The surface of the snow is smoother than that of the gravel; this makes it easier for us to move on snow, as a force acting against our movement is less.
Air/Water resistance: Are the frictional forces of air and water act when an object moves against them? When we are swimming, the force applied in still water is less than when we are moving against the water current.
Why are forces so important? Forces like gravity, friction, pressure are always working on us. We use the force to get some work done. If you remember, the work done was calculated by the following equation.
Work done = Force x Distance.
Where the distance is the distance moved in the direction of the force applied.
But, how can we get this work done? When we apply force to an object, we transfer the energy from one object to another and work gets done.