GK: Class 12 General Q&A · Page 99
3,658 free answers on GK (General) for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
How to calculate work and power
? Work calculation: W = F × d × cos(θ) Power calculation: P = W/t (work per unit time) Or P = F × v (force times velocity) Example: A 500N force moves an object 10m in 5 seconds: Work: W = 500 × 10 = 5,000 J Power: P = 5,000/5 = 1,000 W = 1 kW
- GeneralClass 12All
How to calculate total work hours?
For employee work hours: Daily hours: Subtract start time from end time Subtract breaks: Total time - break time Sum days: Add all daily totals for the period Account for overtime: Separate regular from overtime hours Example: 8 hours/day × 5 days = 40 hours/week
- GeneralClass 12All
What is W equal to?
W can represent different quantities depending on context: Work: W = F × d × cos(θ) (joules) Watt: Unit of power (1 W = 1 J/s) Weight: W = mg (in some contexts) Always check the context to determine whether W represents work, watts, or weight.
- GeneralClass 12All
What is f in stress formula?
In stress calculations, f typically represents: Stress itself: f = F/A (force per unit area) Applied force in some contexts Frequency in dynamic/fatigue analysis Standard stress formula: σ = F/A (Greek sigma for stress, F for force, A for area).
- GeneralClass 12All
Is power P or W?
Power is denoted by P, measured in watts (W): Symbol: P (italicized in equations) Unit: W (watt, upright in text) Formula: P = W/t (work W divided by time) Don't confuse: P (symbol for power) with W (unit watt) and W (symbol for work).
- GeneralClass 12All
What is P in Boyle's law?
. In Boyle's Law, P represents pressure: P₁V₁ = P₂V₂ (at constant temperature) P = pressure (Pa, atm, or mmHg) V = volume (m³ or L) Law states: Pressure and volume are inversely proportional for fixed gas amount at constant temperature
- GeneralClass 12All
What is Delta T = K_f × m?
This is the freezing point depression formula: ΔT = freezing point lowering (°C) K_f = cryoscopic constant (specific to solvent) m = molality of solution (mol/kg) For boiling point elevation: ΔT = K_b × m These colligative properties depend on solute concentration, not identity.
- GeneralClass 12All
What does hψ = Eψ mean?
This is the time-independent Schrödinger equation in quantum mechanics: H = Hamiltonian operator (total energy operator) ψ (psi) = wave function E = energy eigenvalue It describes quantum states where Hψ = Eψ. The wave function ψ contains all information about a quantum system
- GeneralClass 12All
How do mean and median work?
Mean: Sum of values divided by count (average) Formula: (x₁ + x₂ + ... + x_n) / n Affected by extreme values Median: Middle value when data is ordered For odd n: Middle value For even n: Average of two middle values Not affected by extreme values Example for {1, 3, 5, 7, 100}: Mean = 116/5 = 23.2 Median = 5
- GeneralClass 12All
What is the mean of 24 and 36?
Mean = (24 + 36) ÷ 2 = 60 ÷ 2 = 30 The mean (average) of 24 and 36 is 30.
- GeneralClass 12All
How do you find the mean of 1, 2, 3, 4, 5?
Mean = (1 + 2 + 3 + 4 + 5) ÷ 5 Mean = 15 ÷ 5 = 3 The mean of 1, 2, 3, 4, 5 is 3.
- GeneralClass 12All
How does the mean work?
The mean (average) is calculated by: Mean = Sum of all values ÷ Number of values Formula: μ = (x₁ + x₂ + ... + x_n) / n Steps: Add all numbers in the dataset Count how many numbers there are Divide the sum by the count The mean represents the central tendency of data.
- GeneralClass 12All
How to calculate SF and BM?
To calculate shear force and bending moment: Draw free body diagram of the beam Calculate reactions at supports (ΣF = 0, ΣM = 0) Cut sections at points of interest Apply equilibrium: SF: Sum vertical forces BM: Sum moments about cut point Plot SF and BM diagrams Use integration: BM = ∫SF d
- GeneralClass 12All
How to calculate RL of BM?
RL likely refers to Reaction at Left support in beam analysis: Sum all vertical forces: ΣF_y = 0 Take moments about right support: ΣM_R = 0 Solve for R_L (left reaction) Verify: Check with moment about left support Example: Simply supported beam with central load W: R_L = R_R = W/2
- GeneralClass 12All
How to calculate beam size?
Beam sizing involves: Determine loads: Dead load, live load, point loads Calculate maximum BM: From load analysis Select material: Steel, concrete, wood (with allowable stress) Use formula: Section modulus Z = M_max / σ_allowable Choose standard size: Match or exceed required Z Consider deflection limits: δ = (5wL⁴)/(384EI) for
- GeneralClass 12All
What is bending moment (BM) & shear force (SF)?
Shear Force (SF): Internal force parallel to a beam's cross-section, causing sliding Bending Moment (BM): Internal moment causing a beam to bend Relationships: SF = dM/dx (shear force is slope of moment diagram) BM causes stress: σ = My/I Maximum BM occurs where SF = 0 Critical for structural beam design and stress analysis.
- GeneralClass 12All
What is the formula for work and wages?
Wages = Work Hours × Hourly Rate For piece work: Wages = Units Produced × Rate per Unit For salary: Wages = (Annual Salary ÷ Total Work Hours) × Hours Worked Overtime typically pays 1.5× to 2× regular rate depending on regulations.
- GeneralClass 12All
What is the work function φ?
The work function φ (phi) represents the binding energy of electrons at a material's surface. Different materials have different work functions: Sodium: ~2.3 eV Aluminum: ~4.2 eV Gold: ~5.1 eV In the photoelectric effect: hν = φ + KE_max, where hν is photon energy and KE_max is maximum kinetic energy of emitted electrons.
- GeneralClass 12All
Is force a type of work?
No, force and work are distinct concepts: Force is a push or pull (vector, measured in newtons) Work is energy transfer requiring both force AND displacement (scalar, measured in joules) Relationship: Work = Force × Displacement Force can exist without doing work (holding a stationary object). Work only occurs when force causes displacement.
- GeneralClass 12All
Is work function formula?
The work function itself is a property, not a formula. However, related formulas include: Einstein's photoelectric equation: hν = φ + KE_max Threshold frequency: ν₀ = φ/h Threshold wavelength: λ₀ = hc/φ Where h is Planck's constant, ν is frequency, c is speed of light, and φ is the work function. Is power equal to W/t? Yes, <s