Force and Pressure Notes
A force is a push or a pull on an object. This chapter covers how forces change the state of motion or shape of an object, contact forces (muscular, friction) and non-contact forces (magnetic, electrostatic, gravitational), and the idea of pressure including pressure in fluids and atmospheric pressure.
- 3 min read
- 10 practice questions
- Aligned to CBSE 2025–26 syllabus
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- Updated Sept 2026
Use this map for a first read, then return to the checks and formulas during revision.
- 1 key formulas
- 1 concept checks
Force — A Push or a Pull
A force is applied when one object pushes or pulls another. A force always involves an interaction between at least two objects. Force has both magnitude and direction, and when two forces act along the same line, the net force is their sum if they are in the same direction and their difference if opposite.
A force can (1) make a stationary object move, (2) stop a moving object, (3) change the speed of a moving object, (4) change the direction of motion, and (5) change the shape or size of an object.
The state of motion of an object is described by its speed and direction. A force is needed to change this state of motion.
Contact and Non-Contact Forces
Contact forces act only when objects touch. Muscular force is applied by the action of muscles (lifting, pushing a cart). Friction is the force between two surfaces in contact that opposes relative motion.
Non-contact forces act even without touching. Magnetic force acts between magnets and on magnetic materials. Electrostatic force is exerted by a charged body on another charged or uncharged body. Gravitational force is the pull of the Earth (and of every object) — it gives objects their weight and makes things fall.
The pull of gravity acts on every object at all times, which is why a ball thrown up comes back down.
Pressure
Pressure is the force acting on a unit area of a surface. The same force produces a larger pressure when it acts on a smaller area — which is why a sharp knife (small edge area) cuts more easily and why school bags have wide straps (larger area, less pressure on the shoulder).
Liquids and gases exert pressure on the walls of their container and on any object placed in them. Pressure in a liquid increases with depth, which is why dam walls are built thicker at the bottom.
The air around us has weight and exerts atmospheric pressure in all directions. It is large — a rubber sucker sticks to a smooth surface because air pressure outside pushes it in after the air beneath is pushed out.
Force and Pressure: revision sheet
Close the notes and explain each idea in your own words. Then check the formulas and attempt the examples before opening their solutions.
Recall checklist
- Force — A Push or a Pull
- Contact and Non-Contact Forces
- Pressure
For each topic: state the rule, explain when it applies, give an example and identify one mistake to avoid. Return to any topic you cannot explain without looking.
Formula recap (1)
Pressure
Explain your method
Write the given information, choose a method, show the steps, then check units and whether the answer makes sense.
Check worked solution 1
Check worked solution 2
Turn mistakes into revision
Record the question, the step that went wrong and the corrected reason. Try it again tomorrow without the solution, then revisit it after a week. A correct guess still needs an explanation.
Practice and Revision
Test your understanding with quick chapter-level practice.
Chapter Q&A
Does a force always cause motion?
No. A force may only change the shape of an object, or two forces may balance so the object does not move. Motion changes only when there is a non-zero net force.
Why does pressure in a liquid increase with depth?
The deeper you go, the greater the weight of the liquid column above that point pressing down, so the pressure is greater.
Is weight a force?
Yes. Weight is the gravitational force with which the Earth pulls an object towards its centre.