[O] Pure Physics Smart Guides
SECTION I: MEASUREMENT1. Physical Quantities, Units & Measurement7 Topics
SECTION II: NEWTONIAN MECHANICS2. Kinematics8 Topics
3. Dynamics (Forces)7 Topics
4. Mass, Weight & Density4 Topics
5. Turning Effect of Forces4 Topics
6. Energy, Work & Power4 Topics
7. Pressure3 Topics
SECTION III: THERMAL PHYSICS8. Temperature2 Topics
9. Kinetic Model of Matter2 Topics
10. Transfer of Thermal Energy5 Topics
11. Thermal Properties of Matter3 Topics
SECTION IV: WAVES12. General Wave Properties3 Topics
13. Light7 Topics
14. Electromagnetic Spectrum2 Topics
15. Sound5 Topics
SECTION V: ELECTRICITY & MAGNETISM16. Static Electricity5 Topics
17. Current of Electricity3 Topics
18. D.C. Circuits2 Topics
19. Practical Electricity4 Topics
20. Magnetism4 Topics
21. Electromagnetism3 Topics
22. Electromagnetic Induction4 Topics
What is a force?
A force is either a push or a pull that one object exerts on another object.
- Force is a vector quantity
- Force = mass ✕ acceleration
- SI unit of force is Newtons (N) or kg m s⁻²
Different Types of Forces
Contact forces exist between objects that are in contact.
- Applied force:
The push experienced when two objects are pressured together.
- Normal reaction force:
The push exerted by a surface on an object pressing on it. (This push is always perpendicular to the surface).
A force that opposes motion between surfaces in contact.
The pull exerted by a stretched spring, string or rope on an object attached to it.
Non-contact forces do not require objects to be in contact to exist.
- Air/water resistance:
A force that opposes motion due to an object moving in fluid (AKA drag force).
- Gravitational force/weight:
The pull exerted by the earth’s gravity on any object.
- Electric force:
The attractive or repulsive forces between electric charges.
- Magnetic force:
The attractive or repulsive forces between magnets.
Classic Questions of Forces
1. Describe ways in which a force might change the motion of a body.
- A force is may make stationary bodies move.
- A force is may moving bodies speed up, slow down or stop.
- A force is may moving bodies change direction.