Class 11 · Physics · English medium · Part 1
Class 11 Physics Part 1 companion
An interactive companion to Class 11 Physics Part 1: original explanations, motion and force simulations, step-by-step derivations, worked numericals and practice.
An original companion to Physics, NCERT Class 11 Physics (2026–27 edition). Official textbook ↗ ncert.nic.in
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Chapters
- ENHinglish
Chapter 1: Units and Measurement
A measurement compares a quantity with a chosen standard, its unit: a result is a number times a unit. - ENHinglish
Chapter 2: Motion in a Straight Line
Kinematics of motion along a straight line. - ENHinglish
Chapter 3: Motion in a Plane
Vectors have magnitude and direction and add by the triangle or parallelogram law. - ENHinglish
Chapter 4: Laws of Motion
This chapter explains what causes and changes motion. - ENHinglish
Chapter 5: Work, Energy and Power
Class 11 Physics chapter 5 builds the energy approach to mechanics. - ENHinglish
Chapter 6: System of Particles and Rotational Motion
Mechanics is extended from particles to extended bodies. - ENHinglish
Chapter 7: Gravitation
Class 11 Physics chapter 7.
Also in Hinglish
- Chapter 1: Units aur Measurement (Hinglish)
- Chapter 2: Seedhi Line mein Motion (Hinglish)
- Chapter 3: Plane mein Motion (Hinglish)
- Chapter 4: Laws of Motion (Hinglish)
- Chapter 5: Work, Energy aur Power (Hinglish)
- Chapter 6: System of Particles aur Rotational Motion (Hinglish)
- Chapter 7: Gravitation (Hinglish)
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accelerationत्वरणRate of change of velocity with time: average Δ v/Δ t, instantaneous dv/dt; SI unit m s⁻².Ch 2 · Motion in a Straight Lineacceleration due to gravityगुरुत्वीय त्वरणThe acceleration g of a freely falling body; at the Earth's surface g = GME/RE² ≈ 9.8 m/s².Ch 7 · Gravitationangular accelerationकोणीय त्वरणThe rate of change of angular velocity, α = d ω/dt, in rad/s².Ch 6 · System of Particles and Rotational Motionangular momentumकोणीय संवेगThe moment of linear momentum, l = r × p; for a symmetric body turning about its axis, L = I ω.Ch 6 · System of Particles and Rotational Motionangular speedकोणीय चालThe rate of change of the angle swept by the radius, ω = Δ θ/Δ t, in rad/s.Ch 3 · Motion in a Planeangular velocityकोणीय वेगThe rate of change of angular position, ω = d θ/dt, in rad/s; as a vector it points along the axis by the right-hand rule.Ch 6 · System of Particles and Rotational Motionaverage speedऔसत चालTotal path length divided by the time taken; never less than the size of the average velocity.Ch 2 · Motion in a Straight Lineaverage velocityऔसत वेगDisplacement divided by the time taken, v = Δ x/Δ t; the slope of a chord on the x–t graph.Ch 2 · Motion in a Straight LineB
base quantityमूल राशिOne of the seven quantities chosen as independent in the SI, such as length, mass and time.Ch 1 · Units and Measurementbinding energyबंधन ऊर्जाThe energy needed to free a bound body completely; for a satellite in a circular orbit it is GMm/2r.Ch 7 · GravitationC
central forceकेंद्रीय बलA force that always points along the line joining a body to a fixed centre.Ch 7 · Gravitationcentre of gravityगुरुत्व केंद्रThe point about which the total gravitational torque on a body is zero; it is the centre of mass when g is uniform.Ch 6 · System of Particles and Rotational Motioncentre of massद्रव्यमान केंद्रThe mass-weighted average position of a system, R = ∑ mi r i/M. It moves as if all the mass were there and all external forces acted there.Ch 6 · System of Particles and Rotational Motioncentripetal accelerationअभिकेंद्र त्वरणThe acceleration v²/R of uniform circular motion, always pointing towards the centre.Ch 3 · Motion in a Planecentripetal forceअभिकेंद्र बलThe net force towards the centre, of size mv²/R, that keeps a body moving in a circle.Ch 4 · Laws of Motioncoefficient of frictionघर्षण गुणांकFor a pair of surfaces, the ratio of the limiting friction to the normal force: μs for static friction and μk for sliding.Ch 4 · Laws of MotioncomponentघटकThe part of a vector along a chosen axis; Ax = A cos θ can be positive, negative or zero.Ch 3 · Motion in a Planeconservative forceसंरक्षी बलA force whose work depends only on the start and end points, and is zero round any closed path.Ch 5 · Work, Energy and Powercoupleबल युग्मTwo equal and opposite forces with different lines of action. It turns a body without translating it.Ch 6 · System of Particles and Rotational MotionD
derived unitव्युत्पन्न मात्रकA unit made by multiplying and dividing base units, such as m s⁻¹ or the newton.Ch 1 · Units and Measurementdimensional equationविमीय समीकरणAn equation that sets a quantity equal to its dimensional formula, such as [F] = [MLT⁻²].Ch 1 · Units and Measurementdimensional formulaविमीय सूत्रAn expression such as [MLT⁻²] showing which base quantities, with which powers, make up a quantity.Ch 1 · Units and MeasurementdimensionsविमाएँThe exponents that each base quantity carries when a physical quantity is written as a product of base quantities.Ch 1 · Units and Measurementdisplacementविस्थापनThe change in position, Δ x = x2 - x1; its sign gives the direction along the chosen axis.Ch 2 · Motion in a Straight Linedisplacementविस्थापनThe change in position, Δ r = r ' - r, from the initial to the final point, whatever the route.Ch 3 · Motion in a PlaneE
elastic collisionप्रत्यास्थ संघट्टA collision after which the total kinetic energy is the same as before; momentum is conserved too.Ch 5 · Work, Energy and Powerellipseदीर्घवृत्तA closed curve whose points all have the same sum of distances from two fixed points, the foci.Ch 7 · Gravitationequilibriumसाम्यावस्थाThe state of a particle on which the net external force is zero, so that it is at rest or moves with constant velocity.Ch 4 · Laws of Motionescape speedपलायन चालThe least launch speed with which a body can leave a planet's surface and never return, ve = √ 2GM/R.Ch 7 · GravitationF
forceबलA push or pull exerted on a body by another body, measured in newtons. A net force changes the body's velocity.Ch 4 · Laws of Motionfree fallमुक्त पतनMotion under gravity alone, air resistance neglected; near the Earth the acceleration is g ≈ 9.8 m/s² downward.Ch 2 · Motion in a Straight Linefree-body diagramमुक्त पिंड आरेखA sketch of one chosen body or system on its own, showing every external force that acts on it.Ch 4 · Laws of Motionfrictionघर्षणThe component of a contact force that lies along the touching surfaces. It opposes actual or impending sliding between them.Ch 4 · Laws of MotionG
gravitationगुरुत्वाकर्षणThe attraction that every mass exerts on every other mass.Ch 7 · Gravitationgravitational constantगुरुत्वीय नियतांकThe constant G = 6.67 × 10⁻¹¹ N m² kg⁻² in Newton's law of gravitation; it is the same everywhere.Ch 7 · Gravitationgravitational potentialगुरुत्वीय विभवGravitational potential energy per unit mass at a point, V = -GM/r near a mass M, in J/kg.Ch 7 · Gravitationgravitational potential energyगुरुत्वीय स्थितिज ऊर्जाThe work done in bringing masses together slowly from infinite separation; for two masses U = -Gm1m2/r.Ch 7 · GravitationH
horizontal rangeक्षैतिज परासThe horizontal distance a projectile covers before returning to its launch height, v0² sin 2 θ0/g.Ch 3 · Motion in a PlaneI
impulseआवेगThe product of a force and the time it acts, equal to the change in momentum it produces; measured in N s.Ch 4 · Laws of Motioninelastic collisionअप्रत्यास्थ संघट्टA collision in which some kinetic energy is lost; if the bodies stick together it is completely inelastic.Ch 5 · Work, Energy and Powerinertiaजड़त्वThe tendency of a body to resist any change in its state of rest or uniform straight-line motion; mass measures it.Ch 4 · Laws of Motioninstantaneous velocityतात्क्षणिक वेगThe value the average velocity approaches as the time interval shrinks to zero, v = dx/dt; graphically, the tangent slope on the x–t graph.Ch 2 · Motion in a Straight LineJ
jouleजूलThe SI unit of work and energy: the work done when a force of 1 N moves its point of application 1 m along the force.Ch 5 · Work, Energy and PowerK
kinematicsशुद्धगतिकीThe description of motion (position, velocity, acceleration) without asking what causes it.Ch 2 · Motion in a Straight Linekinetic energyगतिज ऊर्जाThe energy of motion, K = 12 mv².Ch 5 · Work, Energy and Powerkinetic frictionगतिज घर्षणFriction between sliding surfaces, fk = μk N, directed against the relative motion.Ch 4 · Laws of MotionL
least countअल्पतमांकThe smallest value an instrument can read directly, such as 1 mm on a school ruler.Ch 1 · Units and MeasurementM
mechanical energyयांत्रिक ऊर्जाThe sum K + V of a body's kinetic and potential energies.Ch 5 · Work, Energy and Powermechanical equilibriumयांत्रिक संतुलनThe state of a rigid body on which both the net external force and the net external torque are zero.Ch 6 · System of Particles and Rotational Motionmoment of inertiaजड़त्व आघूर्णThe rotational inertia of a body about an axis, I = ∑ miri², in kg m².Ch 6 · System of Particles and Rotational MotionmomentumसंवेगThe product of mass and velocity, p = m v, a vector measured in kg m s⁻¹.Ch 4 · Laws of MotionN
newtonन्यूटनThe SI unit of force: the force that gives a mass of 1 kg an acceleration of 1 m/s².Ch 4 · Laws of Motionnormal forceअभिलंब बलThe part of a contact force perpendicular to the surfaces in contact. It adjusts itself to stop one surface moving into the other.Ch 4 · Laws of Motionnull vectorशून्य सदिशThe vector of zero magnitude, 0, with no definite direction.Ch 3 · Motion in a PlaneO
orbital speedकक्षीय चालThe speed of a satellite in a circular orbit of radius r, v = √ GM/r.Ch 7 · Gravitationorder of magnitudeपरिमाण की कोटिThe exponent of the power of ten nearest a value: a × 10 b has order of magnitude b if a ≤ 5 and b + 1 if a > 5.Ch 1 · Units and MeasurementP
path lengthपथ-लंबाईThe total distance actually travelled along the route; never negative and never less than the size of the displacement.Ch 2 · Motion in a Straight LineperihelionउपसौरThe point of a planet's orbit nearest the Sun; the farthest point is the aphelion.Ch 7 · Gravitationpoint objectबिंदु वस्तुA body whose size is negligible compared with the distance it moves in the time studied, so it can be treated as a single point.Ch 2 · Motion in a Straight Lineposition vectorस्थिति सदिशThe arrow from a chosen origin to the point where an object is: r = x i + y j.Ch 3 · Motion in a Planepotential energyस्थितिज ऊर्जाEnergy stored by position or configuration under a conservative force; Δ V = -F Δ x.Ch 5 · Work, Energy and Powerpowerशक्तिThe rate of doing work, P = dW/dt = F · v, measured in watts.Ch 5 · Work, Energy and Powerprinciple of homogeneityविमीय समांगता का सिद्धांतEvery term that is added, subtracted or equated in a valid physical equation has the same dimensions.Ch 1 · Units and Measurementprinciple of momentsआघूर्णों का सिद्धांतFor a lever in equilibrium, load × load arm = effort × effort arm.Ch 6 · System of Particles and Rotational Motionprojectileप्रक्षेप्यAn object in flight after being thrown or launched, moving under gravity alone.Ch 3 · Motion in a PlaneR
radianरेडियनSI unit of plane angle: the angle at the centre of a circle whose arc equals the radius; θ = s/r.Ch 1 · Units and Measurementradius of gyrationघूर्णन त्रिज्याThe distance k from an axis at which the whole mass would give the same moment of inertia: I = Mk².Ch 6 · System of Particles and Rotational Motionreaction timeThe delay between noticing a signal and beginning to respond to it.Ch 2 · Motion in a Straight Linerectilinear motionसरल रेखीय गतिMotion along one straight line, so a single coordinate x gives the position.Ch 2 · Motion in a Straight Linerelative errorआपेक्षिक त्रुटिThe uncertainty of a value divided by the value; multiplied by 100 it is the percentage error.Ch 1 · Units and Measurementrelative velocityसापेक्ष वेगThe velocity of one object as measured from another; along a line, vBA = vB - vA.Ch 2 · Motion in a Straight LineresultantपरिणामीThe single vector equal to the sum of two or more vectors.Ch 3 · Motion in a Planerigid bodyदृढ़ पिंडAn ideal body in which the distance between every pair of particles stays fixed under any forces.Ch 6 · System of Particles and Rotational Motionrolling frictionलोटनिक घर्षणResistance to rolling caused by the slight deformation of a wheel and the surface it rolls on; far smaller than sliding friction.Ch 4 · Laws of MotionS
satelliteउपग्रहA body that orbits a larger body, such as the Moon or an artificial satellite around the Earth.Ch 7 · GravitationscalarअदिशA quantity fully described by a number and a unit, such as mass, time or temperature.Ch 3 · Motion in a Planescalar productअदिश गुणनफलThe product A · B = AB cos θ of two vectors; the result is a scalar.Ch 5 · Work, Energy and Powerscientific notationवैज्ञानिक संकेतनWriting a number as a × 10 b with 1 ≤ a < 10; every digit of a is significant.Ch 1 · Units and Measurementsemi-major axisअर्ध-दीर्घ अक्षHalf the longest diameter of an ellipse, written a; for an orbit it is the average of the nearest and farthest distances.Ch 7 · Gravitationsignificant figuresसार्थक अंकThe digits of a measured value that are known reliably, plus the first uncertain digit.Ch 1 · Units and MeasurementspeedचालThe magnitude of the instantaneous velocity, |v|.Ch 2 · Motion in a Straight Linespring constantस्प्रिंग नियतांकThe constant k in Hooke's law Fs = -kx; it measures stiffness, in N/m.Ch 5 · Work, Energy and Powerstatic frictionस्थैतिक घर्षणFriction between surfaces that are not sliding; it adjusts itself up to a maximum of μs N.Ch 4 · Laws of Motionsteradianस्टेरेडियनSI unit of solid angle: a cone from the centre of a sphere that cuts off an area r² of its surface; Ω = A/r².Ch 1 · Units and Measurementstopping distanceThe distance a vehicle covers from the moment the brakes act until it stops; v0²/2|a| for steady braking.Ch 2 · Motion in a Straight Linesystem of unitsमात्रकों की पद्धतिA complete set of base units together with the derived units built from them, such as CGS, FPS, MKS or SI.Ch 1 · Units and MeasurementT
tensionतनावThe pull exerted by a stretched string, rope or cable. In a massless string it is the same all along its length.Ch 4 · Laws of Motiontime of flightउड्डयन कालThe time a projectile spends in the air before returning to its launch height, 2v0 sin θ0/g.Ch 3 · Motion in a Planetorqueबल आघूर्णThe turning effect of a force about a point, τ = r × F, of size force × moment arm, in N m.Ch 6 · System of Particles and Rotational Motiontrajectoryप्रक्षेप पथThe path followed by a moving object; for a projectile without air drag, a parabola.Ch 3 · Motion in a PlaneU
uniform circular motionएकसमान वृत्तीय गतिMotion along a circle at constant speed; the velocity keeps changing direction.Ch 3 · Motion in a Planeuniformly accelerated motionएकसमान त्वरित गतिMotion whose acceleration keeps the same size and direction, so its v–t graph is straight.Ch 2 · Motion in a Straight Lineunitमात्रकA fixed amount of a quantity, agreed worldwide, that other amounts of the same quantity are compared with.Ch 1 · Units and Measurementunit vectorएकांक सदिशA dimensionless vector of magnitude 1 that only shows a direction, such as i, j, k.Ch 3 · Motion in a PlaneV
vectorसदिशA quantity with magnitude and direction that adds by the triangle law, such as displacement or force.Ch 3 · Motion in a Planevector productसदिश गुणनफलThe vector a × b of size ab sin θ, perpendicular to both vectors, with its sense given by the right-hand rule.Ch 6 · System of Particles and Rotational MotionW
wattवाटThe SI unit of power: one joule per second.Ch 5 · Work, Energy and PowerweightlessnessभारहीनताThe state of a freely falling body, which feels no support force, although gravity still acts on it.Ch 7 · Gravitationworkकार्यDisplacement times the component of the force along it, W = F · d; a scalar measured in joules.Ch 5 · Work, Energy and Powerwork-energy theoremकार्य-ऊर्जा प्रमेयThe net work done by all the forces on a body equals the increase in its kinetic energy.Ch 5 · Work, Energy and Powerncert.ai is an independent learning companion aligned to the NCERT curriculum. It is not affiliated with or endorsed by NCERT.