What is Force?
Definition
A push or a pull acting on an object is called a force.
- SI Unit: Newton (N)
- Named after: Sir Isaac Newton
Examples
- Pushing a box
- Pulling a door to open it
- Kicking a football
What can a Force do?
A Force can-
1.Change the state of motion of an object (make it move, stop, or change speed).
2. Change the direction of a moving object.
3. Change the shape or size of an object.
Examples
- Stopping a moving bicycle — changes its motion
- Squeezing a lemon— changes its shape
- Bending a plastic ruler — changes its shape
- Hitting the ball- Changes its direction
Types of Forces
(a) Contact Forces
These act when two objects are in physical contact.
- 1.Muscular Force: Applied using muscles (e.g. lifting, pushing, kicking).
- 2. Frictional Force: Acts opposite to motion when two surfaces touch.
- Example: Friction between tyres and road.
(b) Non-contact Forces
These forces act without physical contact.
- Gravitational Force: Pull of Earth on all objects towards its centre.
- Example- An apple falling down from the tree
- You jump and come down
- Magnetic Force: Force of attraction/repulsion between magnets.
- South and South Pole or North and North Pole repel each other
- North and South Pole on the two magnets attract each other
- Electrostatic Force: Force between two charged bodies or one charged and other uncharged bodies.
- Examples: Two similarly charged object repel each other. Positive Positive or Negative Negative repel each other
- Positive and Negative attract each other
Test your understanding about the lesson by taking a small quiz. Don’t forget to check back your scores.
[qsm quiz=11]