GK: Class 12 General Q&A · Page 102
3,658 free answers on GK (General) for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What's the difference between speed and velocity?
Speed is a scalar (magnitude only) while velocity is a vector (magnitude and direction). Speed = distance/time Velocity = displacement/time Main differences: Speed is always positive; velocity can be negative (indicating opposite direction) Average speed uses total distance; average velocity uses displacement A car going around a circular track has speed but may have zero average velo
- GeneralClass 12All
How do you find velocity without knowing time?
Use formulas that don't include time: v² = u² + 2as (when you know acceleration and distance) v = √(2gh) (for free fall from height) v = √(2KE/m) (from kinetic energy) v = p/m (from momentum) Note: These energy and momentum approaches are particularly useful in collision problems where time is unknown or irrelevant.
- GeneralClass 12All
What is displacement in physics?
Displacement is a vector quantity that represents the shortest straight-line distance between an object's initial position and its final position, along with the direction of that line. Unlike distance, which measures the total path traveled, displacement only considers where you started and where you ended up. For example, if you walk 10 meters east and then 10 meters west, your total distance is 20 meters, but your displacement is zero because you're back at your starting point.
- GeneralClass 12All
What is the formula for displacement?
The basic displacement formula is: Displacement (s) = Final Position - Initial Position For motion with constant velocity: s = v × t (where v is velocity and t is time) For motion with constant acceleration: s = ut + ½at² (where u is initial velocity, t is time, and a is acceleration) Another common form: s = (u + v)/2 × t (average velocity method)
- GeneralClass 12All
What is the SI unit of displacement?
Q25: The SI (International System) unit of displacement is the meter (m). Since displacement is measured as a length in a specific direction, it uses the same fundamental unit as distance. For larger displacements, kilometers (km) may be used, and for smaller ones, centimeters (cm) or millimeters (mm) are appropriate.
- GeneralClass 12All
What is the difference between distance and displacement?
Distance is a scalar quantity that measures the total path length traveled, regardless of direction. Displacement is a vector quantity that measures the straight-line distance from start to finish with direction. For instance, if you run around a 400-meter track and return to the starting point, your distance is 400 meters, but your displacement is 0 meters. Distance is always positive or zero, while displacement can be positive, negative, or zero depending on the chosen direction.
- GeneralClass 12All
What is the quantity of work?
Work is a scalar quantity that measures energy transfer. It has: Magnitude but no direction Unit: Joule (J) Dimensional formula: [ML²T⁻²] Can be positive (energy added), negative (energy removed), or zero (no displacement or perpendicular force)
- GeneralClass 12All
What are the basic types of work?
The basic types of work in physics include: Positive work: Force and displacement in the same direction (lifting an object) Negative work: Force opposes displacement (friction, air resistance) Zero work: Force perpendicular to displacement (carrying a bag horizontally)
- GeneralClass 12All
What are types of work in physics?
Physics recognizes several work categories: Mechanical work: W = F × d Thermodynamic work: W = -PΔV (pressure-volume work) Electrical work: W = qV (charge times voltage) Gravitational work: W = mgh Spring work: W = ½kx² Rotational work: W = τθ (torque times angular displacement)
- GeneralClass 12All
What are three types of work?
The three fundamental classifications are: Positive Work: Energy is transferred to the system (pushing a cart forward) Negative Work: Energy is removed from the system (applying brakes) Zero Work: No energy transfer despite force application (holding a stationary object)
- GeneralClass 12All
What is a work function in physics?
The work function (φ) is the minimum energy required to remove an electron from a solid's surface to a point just outside. Key points: Symbol: φ (phi) or W Unit: Electron volts (eV) or joules Application: Photoelectric effect, thermionic emission Formula: Energy of incident photon - work function = kinetic energy of ejected electron (hν = φ + KE)
- GeneralClass 12All
Why is W = -PV?
The complete form is W = -PΔV. The negative sign is a sign convention: When gas expands (ΔV positive): System does work on surroundings (W positive) When gas compresses (ΔV negative): Surroundings do work on system (W negative) This convention ensures thermodynamic consistency with the first law: ΔU = Q - W.
- GeneralClass 12All
What is the meaning of W = -PΔV?
This formula represents thermodynamic work in gas processes: W = work done by or on the gas P = pressure (constant for isobaric processes) ΔV = change in volume (V_final - V_initial) Negative sign: Convention where work done BY the system is positive When gas expands (ΔV > 0), work is done by the gas (positive). When compressed (&Delt
- GeneralClass 12All
What is work and force?
Force is a push or pull that can cause an object to accelerate, measured in newtons (N). Work is the energy transferred when a force causes displacement. The relationship is W = F × d. Force is a vector quantity (has direction), while work is a scalar quantity (has magnitude only). Not all forces do work only when they cause displacement.
- GeneralClass 12All
Is work and energy equal?
Work and energy are closely related but not identical. Work is the process of transferring energy, while energy is the capacity to do work. According to the Work-Energy Theorem: Work done on an object equals its change in kinetic energy W = ΔKE = KE_final - KE_initial Energy is conserved; work transforms it from one form to another Both share the same unit (joule) and are scalar quantities.
- GeneralClass 12All
What is the formula and unit of work?
Formula: W = F × d × cos(θ) SI Unit: Joule (J) or Newton-meter (N·m) Dimensional formula: [ML²T⁻²] One joule represents the energy expended when applying a force of one newton through a displacement of one meter.
- GeneralClass 12All
How to get work from kinetic energy?
Using the Work-Energy Theorem, work equals the change in kinetic energy: W = ΔKE = ½m(v₂² - v₁²) Where: m = mass in kilograms v₁ = initial velocity v₂ = final velocity Example: A 2kg object accelerates from 3 m/s to 5 m/s: W = ½ × 2 × (5² - 3²) = 1 × (25 - 9) = 16 joules
- GeneralClass 12All
What is 1 W equal to?
In the context of power, 1 watt (W) equals 1 joule per second (J/s). However, if referring to work, 1 joule is the standard unit. Don't confuse: W (capital) = work measured in joules w (lowercase) sometimes represents work W (in power context) = watts = J/s
- GeneralClass 12All
What is the unit of work?
The SI unit of work is the joule (J), named after physicist James Prescott Joule. One joule is defined as the work done when a force of one newton moves an object one meter in the direction of the force. Other units include: Erg (CGS system): 1 joule = 10⁷ ergs Foot-pound (Imperial system) Kilowatt-hour (kWh) for larger quantities
- GeneralClass 12All
How to calculate work?
To calculate work, follow these steps: Identify the force applied (F) in newtons Measure the displacement (d) in meters Determine the angle (θ) between force and displacement Apply the formula: W = F × d × cos(θ) If force varies, use W = ∫F·ds (integral calculus) For example, if a 10N force moves an object 5m in the same direction: W = 10 × 5 = 50 joules.