General Physics
"Future Physicist/Engineer! Forces and Motion - ang foundation ng lahat ng engineering. F=ma is your best friend! Master the laws of physics para sa college physics at engineering courses!"
1 Vectors vs Scalars
Scalar Quantities
Magnitude only (size/amount)
- • Distance, Speed, Time
- • Mass, Temperature
- • Energy, Work, Power
- Example: "5 meters", "10 kg"
Vector Quantities
Magnitude AND direction
- • Displacement, Velocity, Acceleration
- • Force, Momentum
- • Electric/Magnetic Fields
- Example: "5 m East", "10 N upward"
Vector Components:
Vx = V cos θ | Vy = V sin θ | V = √(Vx² + Vy²)
2 Kinematics - Motion in One Dimension
Kinematic Equations (UAM)
Uniformly Accelerated Motion (constant acceleration)
Key Terms
- v₀: Initial velocity
- v: Final velocity
- a: Acceleration
- t: Time
- x: Displacement
Free Fall
- g = 9.8 m/s² (or ~10)
- Downward = positive g
- Upward = negative g
- At highest point: v = 0
Projectile Motion
- Horizontal: constant v
- Vertical: free fall (g)
- Range = v₀²sin(2θ)/g
- Max at θ = 45°
3 Newton's Laws of Motion
First Law (Inertia)
An object at rest stays at rest, an object in motion stays in motion (unless acted upon by an external force).
Example: You lurch forward when a car stops suddenly
Second Law (F = ma)
F = ma
Force equals mass times acceleration. Unit: Newton (N) = kg·m/s²
More force = more acceleration (for same mass)
Third Law (Action-Reaction)
For every action, there is an equal and opposite reaction.
Example: Rocket pushes gas down, gas pushes rocket up
4 Work, Energy, and Power
| Quantity | Formula | Unit | Notes |
|---|---|---|---|
| Work | W = Fd cos θ | Joule (J) | Force × displacement in direction |
| Kinetic Energy | KE = ½mv² | Joule (J) | Energy of motion |
| Potential Energy | PE = mgh | Joule (J) | Energy due to height |
| Power | P = W/t = Fv | Watt (W) | Rate of doing work |
Conservation of Energy:
Total mechanical energy (KE + PE) is constant in a closed system (no friction)
KE₁ + PE₁ = KE₂ + PE₂
5 Momentum and Impulse
Momentum (p)
p = mv
- Unit: kg·m/s
- Vector quantity
- More mass or velocity = more momentum
Impulse (J)
J = FΔt = Δp
- Unit: N·s = kg·m/s
- Change in momentum
- Airbags: increase Δt, decrease F
Conservation of Momentum:
m₁v₁ + m₂v₂ = m₁v₁' + m₂v₂'
Total momentum before = Total momentum after (in collisions)
6 Circular Motion and Gravitation
Circular Motion
- Centripetal Acceleration: ac = v²/r
- Centripetal Force: Fc = mv²/r
- Period: T = 2πr/v
- Direction: Always toward center
Newton's Law of Gravitation
F = Gm₁m₂/r²
- G: 6.67 × 10⁻¹¹ N·m²/kg²
- Inverse square law
- Double distance = 1/4 force
7 Waves and Basic Optics
Wave Equation
v = fλ
- v: wave speed (m/s)
- f: frequency (Hz)
- λ: wavelength (m)
- Period: T = 1/f
Wave Types
- Transverse: Perpendicular motion (light, water)
- Longitudinal: Parallel motion (sound)
- Sound speed: ~343 m/s in air
- Light speed: 3 × 10⁸ m/s
Light and Optics
Practice Questions
1. A 5 kg object accelerates at 2 m/s². What is the net force?
Show Answer
10 N. Using F = ma: F = (5 kg)(2 m/s²) = 10 N.
2. An object falls from 20 m. What is its speed just before hitting the ground?
Show Answer
~20 m/s. Using v² = v₀² + 2ax: v² = 0 + 2(10)(20) = 400, so v = 20 m/s.
3. What is the kinetic energy of a 2 kg ball moving at 4 m/s?
Show Answer
16 J. Using KE = ½mv²: KE = ½(2)(4)² = ½(2)(16) = 16 J.
4. A wave has frequency 100 Hz and wavelength 2 m. What is its speed?
Show Answer
200 m/s. Using v = fλ: v = (100 Hz)(2 m) = 200 m/s.
Exam Tips for General Physics
- ✓ F = ma is the most important equation - know it well!
- ✓ Units matter: Always check that your units make sense
- ✓ Draw diagrams: Free body diagrams help visualize forces
- ✓ Conservation laws: Energy and momentum are conserved in closed systems
- ✓ g = 10 m/s² is often used for easier calculation (actual: 9.8)
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