a full brief summary of class 8 physics cbse ncert lesson: force and pressure hoping for a answer fast.. thank you
Answers
Answer:
Force:
(i) Force is a push or a pull.
(ii) Living and non- living things can apply force.
(iii) To apply a force over an object interaction between object and source of force is necessary.
(iv) Whenever force act two object are involved. One which applied force, the other which receive force.
Examples: To kick ball we need to push it, to pick the book we need to pull it, to hit the ball we need to push it and to lift the box we need to push iI.
rolling pin.
So we can say that forces can change the shape of an object.
Types of Force:
1. Contact Force:
(a) For contact force, interaction between objects is necessary. Force that comes into action after the interaction between objects is called contact force. Contact force works on the point of contact. Example; pushing a car, hitting the ball, kicking a ball, etc.
(b) Muscular force, friction force are types of contact force.
(a) Muscular force:
(i) Force due to the action of muscles is called muscular force. We can say force resulting because of action of muscle is called muscular force.
(ii) Muscular force is applied only after interaction with the object.
Examples:
(a) When we push the object like school bag or lift the bucket of water we use the muscular force.
(b) Animals also use of muscular force to carry out their task.
(b) Friction Force:
(i) The forces of friction arises between the surfaces of two objects
(ii) The force of friction always acts on all moving object and its direction is always opposite to the direction of motion.
(iii)Force of friction comes into action only after interaction between two objects, thus, it is a type of contact force.Examples:
(a) Due to force of friction between the surface of the ball and the ground that brings the moving ball to rest.
(b) When we stop pedalling a bicycle, it gradually slow down and finally comes to s stop due to force of friction.
2. Non- Contacting Force:
(i) Force due to without interaction between two objects is called non-contact force. For example; a magnet can pull an iron nail from a distance.
(ii) Magnetic force, Electrostatic force and Gravitational force are examples of non-contact force.
(a) Magnetic Force:
(i) A magnet can exert a force on another magnet without being in contact with it.
(ii) The force exerted by a magnet is an example of a non-contact force.
Example: Opposite pole of two magnets attract each other and same pole repel each other.
(b) Electrostatic Force:
(i)When a charged body exert a force on another charged or uncharged body is called electrostatic force.
A charged body attracts an uncharged body.
(ii) A positively charged body attracts a negatively charged body and repels a positively charged body without coming in contact, thus it is a non-contact force.
(c) Gravitational Force:
(i) Gravitation force is exerted by earth, moon, sun and other planets to ot
Answer:
.Force brings about a change in the direction or state of motion of a body.
Push
A push is a force exerted away from the body, e.g: Hitting a snooker ball, kicking a football.
Pull
A pull is a force exerted towards the body, e.g: drawing a bucket of water from a well, playing tug of war.
Force acting per unit area is known as pressure.
P=forcearea
SI unit is Pascal.