PHYSICS LECTURE

PHYSICS LECTURE: MEASUREMENT & MOTION

1. Length, Area and Volume

SI unit of length = metre (m)

Vernier Calipers Example

Main scale reading = 2.3 cm
Vernier reading = 0.07 cm
Total length = 2.3 + 0.07 = 2.37 cm

Micrometer Screw Gauge Example

Pitch = 0.5 mm, Head scale = 25 divisions
Reading = 2.5 mm + (25 × 0.01) = 2.5 + 0.25 = 2.75 mm

Volume Calculation

Cube of side 4 cm
Volume = 4 × 4 × 4 = 64 cm³

2. Mass

SI unit = kilogram (kg)

If object balances with 200g + 50g weights,
Mass = 250 g

3. Time

SI unit = second (s)

Time taken for 20 oscillations = 40 s
Period = 40/20 = 2 s

4. Fundamental & Derived Quantities

Fundamental: Length, Mass, Time

Derived: Velocity, Density

Density = Mass/Volume
= 2kg / 0.5m³ = 4 kg/m³

5. Dimensions

Velocity = m/s = LT⁻¹

6. Errors & Significant Figures

Measured length = 5.2 cm ± 0.1 cm

7. Scalars and Vectors

Scalar: speed, mass

Vector: velocity, force

Resolve 10N at 30°:
Horizontal = 10cos30 = 8.66N
Vertical = 10sin30 = 5N

8. Motion

Types: translational, rotational, oscillatory

9. Linear Motion

Use equation v = u + at
u = 0, a = 2m/s², t = 5s
v = 0 + (2×5) = 10 m/s

s = ut + 1/2 at²
s = 0 + 1/2 × 2 × 25 = 25 m

10. Projectile Motion

Velocity = 20m/s at 30°
Time of flight = (2u sinθ)/g = (2×20×0.5)/10 = 2 s

Range = (u² sin2θ)/g = (400 × sin60)/10 = 34.6 m

11. Newton's Laws

F = ma
F = 5kg × 2m/s² = 10 N

Momentum = mv = 2kg × 3m/s = 6 kgm/s

12. Circular Motion

Centripetal force = mv²/r
= 2×(4²)/2 = 16 N

13. Simple Harmonic Motion

T = 2π√(l/g)
l = 1m
T = 2×3.14×√(1/10) = 2 s approx