General Awareness
Physics Guide & Practice
Study Newton's laws, optics, heat, electricity, and scientific laws for SSC, Banking and NDA exam General Awareness sections. Explore dynamic solver blueprints, master fundamental equations, examine step-by-step solved examples, and practice with real exam-grade mock test sets.
Practice Question Papers
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1. Fundamentals & Definitions
| Term | Definition |
|---|---|
| Scalar Quantity | A physical quantity that has only magnitude but no direction. Examples: mass, speed, distance, time. |
| Vector Quantity | A physical quantity that has both magnitude and direction. Examples: velocity, displacement, force, acceleration. |
| Distance | The total path length covered by an object. It is a scalar quantity. |
| Displacement | The shortest distance between the initial and final positions of an object. It is a vector quantity. |
| Speed | The rate of change of distance. (Speed = Distance / Time). It is a scalar quantity. |
| Velocity | The rate of change of displacement. (Velocity = Displacement / Time). It is a vector quantity. |
| Acceleration | The rate of change of velocity. (Acceleration = Change in Velocity / Time). It is a vector quantity. |
| Force | A push or pull on an object that can cause it to change its state of motion. (F=ma). It is a vector quantity. |
| Inertia | The property of a body to resist any change in its state of rest or of uniform motion. |
| Momentum | The product of an object's mass and velocity (p = mv). It is a vector quantity. |
| Work | Done when a force causes a displacement of an object. (Work = Force × Displacement). It is a scalar quantity. |
| Energy | The capacity to do work. Main forms are Kinetic Energy (energy of motion) and Potential Energy (stored energy). |
| Power | The rate at which work is done or energy is transferred. (Power = Work / Time). |
| Circular Motion | The movement of an object along the circumference of a circle or rotation along a circular path. |
| Centripetal Force | A force that acts on a body moving in a circular path and is directed towards the center around which the body is moving. |
| Heat | A form of energy that is transferred between systems or objects with different temperatures. |
| Temperature | A measure of the average kinetic energy of the atoms or molecules in a system. |
| Conduction | The process of heat transfer through a substance from a region of higher temperature to a region of lower temperature without any actual movement of the particles. |
| Convection | The mode of heat transfer by the actual bulk movement of matter. It occurs in fluids (liquids and gases). |
| Radiation | The mode of heat transfer that does not require a medium. Heat is transferred in the form of electromagnetic waves. |
| Latent Heat | The heat energy which has to be supplied to a body to change its state without any rise in its temperature. |
| Light | A form of electromagnetic radiation that is visible to the human eye. |
| Rectilinear Propagation | The property of light to travel in a straight line in a homogenous medium. |
| Reflection | The bouncing back of light when it strikes a smooth, polished surface. |
| Refraction | The bending of light as it passes from one medium to another. |
| Refractive Index | A value calculated from the ratio of the speed of light in a vacuum to that in a second medium of greater density. |
| Mirror | A polished surface that reflects light to form an image. Can be plane or spherical (concave/convex). |
| Lens | A transparent optical device with two curved surfaces that converges or diverges light rays. Can be concave or convex. |
2. Core Concepts & Formulas
Motion
| Concept | Formula | Variables |
|---|---|---|
| Equations of Motion | 1. v = u + at 2. s = ut + (1/2)at² 3. v² = u² + 2as | v=final velocity, u=initial velocity, a=acceleration, t=time, s=displacement |
| Newton's Second Law | F = ma | F=force, m=mass, a=acceleration |
| Momentum | p = mv | p=momentum, m=mass, v=velocity |
| Work Done | W = Fd cos(θ) | W=work, F=force, d=displacement, θ=angle between F and d |
| Kinetic Energy | KE = (1/2)mv² | KE=kinetic energy, m=mass, v=velocity |
| Potential Energy | PE = mgh | PE=potential energy, m=mass, g=gravity, h=height |
| Power | P = W/t | P=power, W=work, t=time |
| Centripetal Force | Fc = mv²/r | Fc=centripetal force, m=mass, v=velocity, r=radius |
Light (Optics)
| Concept | Formula | Variables |
|---|---|---|
| Snell's Law of Refraction | n₁ sin(θ₁) = n₂ sin(θ₂) | n=refractive index, θ=angle of incidence/refraction |
| Refractive Index | n = c/v | n=refractive index, c=speed of light in vacuum, v=speed of light in medium |
| Mirror Formula | 1/f = 1/v + 1/u | f=focal length, v=image distance, u=object distance |
| Lens Formula | 1/f = 1/v - 1/u | f=focal length, v=image distance, u=object distance |
Heat (Thermodynamics)
| Concept | Formula | Variables |
|---|---|---|
| Temperature Conversion | C/5 = (F - 32)/9 | C=Celsius, F=Fahrenheit |
| Specific Heat Capacity | Q = mcΔT | Q=heat energy, m=mass, c=specific heat, ΔT=change in temp |
| Latent Heat | Q = mL | Q=heat energy, m=mass, L=specific latent heat |
| Newton's Law of Cooling | dT/dt = -k(T - Tₛ) | T=object temp, Tₛ=surrounding temp, k=constant |
| Laws of Thermodynamics | Zeroth: If two systems are in thermal equilibrium with a third, they are in thermal equilibrium with each other. First: Energy cannot be created or destroyed (Law of Conservation of Energy). ΔU = Q - W. Second: The total entropy of an isolated system can only increase over time. | ΔU=change in internal energy, Q=heat added, W=work done |
Typical Exam Weightage
| Exam | Typical Questions |
|---|---|
| SSC (CGL / CHSL / MTS) | 2–3 questions |
| Railways (RRB) | 3–4 questions |
| Defense (NDA / CDS) | 2–3 questions |
Units, everyday mechanics (motion, force, simple machines), and basic electricity concepts are tested most often.
Figures are typical ranges based on recent-year patterns, not a guarantee for any specific upcoming paper — always cross-check against the latest official syllabus and previous-year papers for Physics.
Solved Examples
1Easy
Question: Which one of the following is not a periodic motion?
- Rotation of the earth about its axis.
- A freely suspended bar magnet.
- The motion of hands of a clock.
- An arrow released from a bow.
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Step-by-Step Explanation
- Periodic motion is a motion that repeats itself in equal intervals of time.
- 1, 2, and 3 (rotation of Earth, a swinging magnet, and clock hands) are all examples of motion that repeat over a regular period.
- 4, an arrow released from a bow, travels in a projectile path and does not repeat its motion. It's a one-time event.
- Therefore, the correct answer is 4.
2Moderate
Question: Which of the following is a condition for the interference of light waves?
- The source must be monochromatic.
- Coherent source of light.
- Sources must have the same state of polarisation.
- All of the above.
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Step-by-Step Explanation
- Interference is the phenomenon where two waves superpose to form a resultant wave of greater, lower, or the same amplitude.
- For sustained and observable interference of light, several conditions must be met:
- Coherent Sources: The sources must emit waves with a constant phase difference.
- Monochromatic Light: The waves should ideally be of a single wavelength (or very narrow band of wavelengths). This creates clear and distinct interference patterns.
- Same State of Polarisation: The light waves must be polarised in the same plane.
- Since all listed conditions are necessary for stable and clear interference, the correct option includes all of them.
- Therefore, the correct answer is 4.
3Hard
Question: Consider a collection of a large number of particles, each moving with a speed v. The direction of velocity is randomly distributed in the collection. The magnitude of the relative velocity between a pair of particles averaged over all the pairs in the collection is:
v2v/ππv/44v/π
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Step-by-Step Explanation
- Let two particles have velocities
v₁andv₂. Since the speed is the same for all,|v₁| = |v₂| = v. The directions are random. - The relative velocity is
v_rel = v₁ - v₂. - The magnitude of the relative velocity is
|v_rel| = |v₁ - v₂|. - Using the law of cosines,
|v_rel|² = |v₁|² + |v₂|² - 2(v₁ ⋅ v₂) = v² + v² - 2v²cos(θ) = 2v²(1 - cos(θ)), whereθis the angle betweenv₁andv₂. - So,
|v_rel| = v * sqrt[2(1 - cos(θ))]. Using the half-angle identity1 - cos(θ) = 2sin²(θ/2), this simplifies to|v_rel| = 2v |sin(θ/2)|. - We need to find the average value of this quantity over all possible random directions. For a uniform distribution of directions in 3D space, the probability distribution of the angle
θbetween two random vectors is proportional tosin(θ). - The average is calculated by the integral:
<|v_rel|> = ∫[2v sin(θ/2) * (1/2)sin(θ) dθ]from 0 to π. - Let's consider a simpler, more common approach for this exam level, often seen in 2D analysis. The average value of the relative velocity magnitude between two particles moving randomly in a plane is given by the integral
<|v_rel|> = (1/π) ∫ |v₁ - v₂| dθfrom 0 to π. - This evaluates to
(4/π)v. This is a standard result in the kinetic theory for 2D gases. Given the options, this is the most probable intended answer. - Therefore, the correct answer is 4.