Physics Basics for CSIR‑NET (General Awareness & Current Affairs)
Prepared for students aiming to excel in the CSIR‑NET GA & CA paper.
Why Physics?
The CSIR‑NET GA/CA section tests a broad understanding of science, and physics is the backbone of many current‑affairs topics – from gravitational‑wave detectors to quantum‑computing breakthroughs. Mastering the fundamentals will help you answer conceptual questions, solve quantitative problems, and connect physics to recent research.
1. Kinematics (1‑D & 2‑D)
| Symbol | Meaning | Units |
|---|---|---|
| (v) | velocity | m s⁻¹ |
| (a) | acceleration | m s⁻² |
| (x) | displacement | m |
| (t) | time | s |
1‑D Equations of Motion (constant (a))
[ \begin{aligned} v &= u + a t \ x &= u t + \tfrac{1}{2} a t^{2} \ v^{2} &= u^{2} + 2 a x \end{aligned} ]
Derivation (example)
From (a = \dfrac{dv}{dt}) and (v=\dfrac{dx}{dt}),
[ a = \frac{dv}{dx}\frac{dx}{dt} ;\Rightarrow; a, dx = v, dv ]
Integrating from (u) to (v):
[ \int_{u}^{v} a,dx = \int_{u}^{v} v,dv ;\Rightarrow; a x = \tfrac{1}{2}(v^{2}-u^{2}) ]
Rearrange to obtain (v^{2}=u^{2}+2ax).
2‑D Projectile Motion (no air resistance)
[ \begin{aligned} x(t) &= v_0\cos\theta,t \ y(t) &= v_0\sin\theta,t - \tfrac{1}{2}gt^{2} \end{aligned} ]
- Range (R = \frac{v_0^{2}\sin 2\theta}{g})
- Maximum height (H = \frac{v_0^{2}\sin^{2}\theta}{2g})
2. Newton’s Laws
| Law | Statement | Key Equation |
|---|---|---|
| 1st | Inertia | (m\mathbf{a} = \mathbf{0}) if no net force |
| 2nd | Dynamics | (\boxed{\mathbf{F}_{\text{net}}=m\mathbf{a}}) |
| 3rd | Action‑reaction | (\mathbf{F}{12}=-\mathbf{F}{21}) |
Tricky Point
- Direction: The vector equation keeps track of the sign; always write (\mathbf{F}_{\text{net}}) as a sum of all component forces.
3. Work, Energy, Power
| Symbol | Meaning | Units |
|---|---|---|
| (W) | Work | J |
| (K) | Kinetic energy | J |
| (U) | Potential energy | J |
| (P) | Power | W |
Work–Energy Theorem
[ W_{\text{net}} = \Delta K = \frac{1}{2}m(v^{2}-u^{2}) ]
Derivation
(W = \int \mathbf{F}\cdot d\mathbf{r}). Using ( \mathbf{F}=m\mathbf{a} ) and ( \mathbf{a}=\frac{d\mathbf{v}}{dt}):
[ W = m\int \frac{d\mathbf{v}}{dt}\cdot d\mathbf{r}