Force 

What is Force ? 

• A force is a push or pull upon an object which results from the object’s interaction with another object.
•  Whenever there is an interaction between two objects, there is a force upon each of the objects.
•  When this  interaction stops, the two objects no longer experience the force. 
• Forces only exist as a result of an interaction.

Effects Of Force On An Object

A push or a pull acting on an object is called force.

 The action of a force can cause

(a) a stationary object to move,

E.g: A car can be made to move by giving it a little push.

(b) a moving object to change its speed or stop

E.g: A bicycle can be stopped or slowed down by applying the brakes.

(c) a moving object to change its direction of motion,

E.g:  In football, the players can change the direction of the moving ball by kicking it in a different direction. 

(d) an object to change in size and shape

E.g: We can change the shape of clay to make objects of different shape and sizes

Types of Force

Muscular Force

When you push or pull an object, you use your muscles to apply force. This force is called muscular force. You use muscular force to open a door, move a table, write in your notebook and so on. 

 

Gravitational Force

 Every object in the universe attracts the objects near it. This force of attraction is called gravitational force. It depends on the size of the object. Have you seen how a ball that is thrown up falls back to the Earth? It is Earth’s gravity that pulls objects towards the Earth and keeps them from flying away into space.

Define gravity.

Gravity means force of attraction between earth and any other object.  Gravitational force is exerted by all the objects but gravity is exerted only by the earth.

 

Frictional Force 

Have you seen what happens when a toy car is pushed? The car stops after some time. This is because of friction.

Define friction

• The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it.
•  It acts in the direction opposite to the direction of movement and stops the car after some time. Smooth surfaces cause less friction than rough surfaces. Friction is very important in daily life. It is needed for you to walk on any surface. 

Elastic Force

 What happens when you stretch a rubber band and let it go? It gets  back to its original length. It is due to elastic force.

 Elastic force is the force which  resists the change in shape in an elastic material   when it is  stretched or compressed.

Mechanical Force 

This is a kind of force that causes the  object on which it acts to change its motion or start moving. It can also  bend or break things. 

Example: Pulling water from well needs mechanical force.

Force And Work

You do work when you push a cart. You have to use force to do this work. This shows that you have to apply force to do work. However, you use less force to move an empty cart and more force to move a cart full of things. 

So, less force is used to do less work. 

More force is used to do more work. 

Also Check –Weight volume And Density Class 5 – Notes

Work

A work is said to be done when a force applied on an object causes it to move a certain distance in the direction of force.

Examples of work done:

•  pulling or pushing a cart through some distance 
• Carrying a load up a staircase pushing and moving a box up a ramp
•  Running or jogging 
•  Playing outdoor sports such as football and badminton 
•  Swimming 

Examples of work not being done 

•  Reading a book or studying for an examination 
•  Holding a heavy load, but not moving
•  Pushing a heavy box or wall that does not move 

Although reading a book involves a lot of mental work, it will not be considered physical work. Similarly, if someone holds a heavy load but does not move through .

Energy

What is Energy 

Energy is defined as capacity or ability to do work.

• Work and Energy are closely related to each other.
• Whenever work is done , there is always a change or transfer of energy.
• Energy is needed to the work.

Also Check –

Check – Difference Between work And energy

Renewable And Non Renewable Energy

• The energy sources that last for a long period of time, such as sun, water or wind are called renewable energy sources.
• The energy we get from these sources is known as renewable energy. 
• Example: Solar energy, hydro energy (energy of moving water), and wind energy are examples of renewable energy.

•   The energy sources that are present in limited amount in nature and do not disappear for a long period of time. These are called non-renewable energy sources.

• The energy that we get from these sources is known as non-renewable energy
• They cannot be easily made by natural means so we should use them judiciously and carefully.

Examples of such sources are coal, petroleum, and natural gas.