Class 8 Science Lesson 11 Inside Question and Answer NCERT & CBSE Board Here in this post. NCERT Class 8 Science Textbook Lesson 11 Inside Questions.
- Grade: VIII
- Lesson 11 Force and Pressure
Que. 1) fill in the blanks.
(1) A push pr a pull on an object is called —-
Ans- force
(2) —- expressed the strength of a force.
Ans- magnitude
(3) The force acting on a unit area of a surface is called —-
Ans –Pressure
(4) The state of motion of an object is described by it’s —– and —-
Ans- speed and direction of motion.
Que. 2) Write answers of the following questions.
(1) Define the followings-
Force- a push or a pull on an object is called a Force.
Muscular force-the force resulting due to the action of muscles is known as muscular force.
Contact force-The muscular force can be applied only where it is contact with an object then this muscular contact is also known as contact force.
Electrostatic force – The forced exerted by a charged body on another charged or uncharged body is known as Electrostatic force.
Atmospheric pressure-the atmospheric air extends up to many kilometers above the surface of the earth ,the pressure exerted by this air is known as Atmospheric pressure.
Gravitational force- every object in the universe whether small or large exerts a force on every other objects, this force is known as gravitational force.
(2) A force can change the state of motion? Explain.
Ans- a force can change the state of an object or motion. For eg. While taking a penalty kick in football , the player applies a force on the ball . before being hit, the ball was at rest and so its speed was zero. The applied force makes the ball move towards the goal and goal kipper jumps to save goal he tries to apply a force on the moving ball. It means if the force applied on the object then it is change the state of motion of an object.
(3) What is state of motion?
Ans- The state of motion of an object is described by its speed and the direction of motion. The state of rest is considered to be the state of zero speed. An object may be at rest or in motion both are its state of motion.
(4) Why porters place around piece of clothe on their head?
Ans- porters place around a piece of clothe on their head because when they have to carry heavy loads by doing this they increases the area of contact of the load with their head. So the pressure on their head is reduced and they find it easier to carry the load.
(5) Give any two examples of pull and push situations.
Ans- pull or push a door, push a car, push a bed, pull a rope etc.
Que. 3) Write short note on followings.
1) Pressure– the force acting on a unit area of a surface is called pressure. Pressure = force /area on which it acts. The fore is which act perpendicular to the surface on which the pressure is to be computed. For eg. Pushing a nail into wooden blank by its pointed end for this work we have force and pressure then it is done.
2) Atmospheric pressure–the atmospheric air extends up to many kilometers above the surface of the earth. The pressure exerted by this air is known as atmospheric pressure. For example. Imagine a unit area and a very long cylindrical standing on it filled with air then the force of gravity on the air in this cylinder is the atmospheric pressure.
3) Gravitational force–Gravitational force is an attractive force which attracts all object toward earth. The gravitational force acts on all of us. Every object in the universe , wheather small or large exerts a force on every other object and this force is known as gravitational force.