Force and Energy
Concept: Force—Effects and Types
What is force?
A push or pull acting on any object is considered a force. It makes things move or make them change their state of motion.
Effects of force:
Force has the following effects on objects—
- It can stop a moving object and vice versa.
- It can change the direction of a moving object.
- It can change the shape of an object.
Types of forces:
- Contact force:
- Frictional force: It is the force exerted due to friction.
- The force exerted by friction always acts in the opposite direction of the motion.
- Smooth surfaces cause less friction, and rough surfaces cause more friction.
- Frictional force plays a role in almost everything we do in our daily lives.
- Writing on a paper.
- Walking or running on the road.
- Holding a glass of water.
- Mechanical force:It is the force exerted by machines.
- Movement of a pulley while riding a bicycle.
- Rotation of a wheel while dragging a trolley.
- Rotation of a blade while operating a grinder.
- Muscular force:It is the force exerted by virtue of muscles.
- Lifting a heavy object.
- Kicking a football.
- Elastic force: It is the force exerted by a deformed object when it tries to return to its original position.
The force that acts only when two surfaces come in contact with each other is called a contact force. Contact forces are further classified as shown below—
- A stretched rubber band gaining its original shape.
The forces which can act between two objects even if the surfaces are away from each other are called non-contact forces. Non-contact force is further classified as shown below—
- Magnetic force: The force exerted by a magnet in the form of attraction or repulsion is called magnetic force.
- Magnetic objects are attracted to a magnet.
- Examples: Iron
- Unlike poles of a magnet attract each other whereas like poles repel each other.
- In winters, we often feel a mild current, the sensation of a crackling sound when we wear woollen clothes or touch any metal object. It happens because of the development of an electrostatic charge on our body.
- The same can be tried by rubbing a comb against the hair and then bringing the comb near small pieces of paper. The paper pieces get attracted to the comb.
There can be more than one force acting at a time. Look at the examples given below to understand.
- Writing on a piece of paper involves both frictional and muscular force.
- Muscular: Holding the pencil/pen with fingers and using the hand for writing.
- Frictional: The force acting between the tip of the pencil/pen and the paper.
- Mechanical: A pulley is a simple machine attached to the well. Its function is to facilitate the easy movement of the rope. Hence, the mechanical force comes into play.
- Frictional: The force applied by the person using their hands to pull the bucket of water with the help of the rope.
- Elastic: The force exerted by the rubber of the bow when the archer stretches it is the elastic force.
- Mechanical: The force applied by the person using their hands to pull the rubber and the arrow constitutes the mechanical force.
Attractive force: It is the force that draws one object towards another..
Repulsive force: It is the force that makes one object move away from another.
Gravity: It is the force by virtue of which a planet or any other body can draw objects toward its centre.
Did You Know?
- Water spilled on a marble floor decreases its friction, making us fall easily on such a floor.
- We would not be able to stand on Earth if there was no gravitational force.
- Sir Isaac Newton was the first scientist who studied gravity and force.
- Air tries to decrease the speed of any moving object in it by friction. This frictional force exerted by air is called drag.