1. Indus International School, Bangalore
Concept of Force
Indus International School, Bangalore

2. Force A Force is something which causes an object to:
1. Change its shape
2. Speed up
3. Slow down Acceleration
4. Change direction

3. Force is a Vector
Force can produce acceleration – it is a Vector quantity.
Resultant of Forces: If two or more forces acting on a particle, the net force experienced by the particle is the Resultant.
The diagrams which represent the forces acting on a body or particle are called “Free Body Diagrams” R P θ Q

4. Free body diagram The diagram at right shows all the
force acting on this block.
Here we have Gravity, Frictional
Force, Applied Force, and Normal
Force acting on this block.
Objects can have any number of
forces acting on them, depending on
the situation.

5. Forces acting on a car
As shown in the free body diagram below, there are six forces acting on the vehicle:
Rolling Resistance
Aerodynamic Drag
Aerodynamic Lift
Gravity
Normal
Motor

6. When a cord (or other such objects) is attached to a body
Tension
When a cord (or other such
objects) is attached to a body
and pulled taut, the cord pulls
on the body with a force T
directed away from the body
and along the spring.
This force is called a Tension Force because the cord is said to be under tension.

7. Tension in spring When a spring is pulled, a tension
force is produced in the spring.
This force opposes the pulling
force and equal in magnitude with
that.
If force ‘F’ is plotted against
extension ‘e’, F is directly
Proportional to e to some point. After
that, the proportionality is lost.
F = k x . where ‘k’ is called spring constant.
F/N
X .
e/m

8. Types of Forces – 4 fundamental forces
Gravitational Forces:
- This force acts between all the particles in the universe.
- This also gives rise to the weight of an object.
Weak- Interaction:
- A force which is about times stronger than gravity.
- This force is experienced by certain aspects of radioactive decay of nuclei.

9. Types of Forces (contd.)
Electromagnetic Interaction:
- The electromagnetic interaction is some 1037 times stronger than gravity.
- This force exists between particles as a result of the electrical charge that they carry.
Strong Nuclear Interaction:
- The interaction is some 1039 times stronger than gravity.
- This force holds the protons and neutrons together in a nucleus.