# Motion in a Plane Notes, Class 11 Physics | SwaVid Motion in a Plane, NCERT Class 11 Physics: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-11/physics/chapter/motion-in-a-plane Source: https://www.swavid.com/cbse/class-11/physics/chapter/motion-in-a-plane # Motion in a Plane ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 11 Physics on SwaVid ### Scalars and vectors ### Vector addition and resolution ### Position, velocity, and acceleration ### Projectile motion ### Uniform circular motion ### Next chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 11 › Physics › Motion in a Plane Notes written by SwaVid from the NCERT textbook. Class 11 Physics, Chapter 3. Key ideas, formulas and common mistakes. CBSE prints 23 marks for Units I-III together, not for this chapter alone. Short answer. This chapter covers two-dimensional kinematics using vectors, resolving motion into perpendicular components, projectile motion, and uniform circular motion. It shows that two-dimensional motion can be treated as two independent, simultaneous one-dimensional motions along perpendicular axes. Source: NCERT Physics Part I (Reprint 2026-27) , Chapter 3, Motion in a Plane Scalars are physical quantities that have only magnitude, while vectors possess both magnitude and direction and obey vector algebra. Vectors are represented by bold letters or an arrow over the symbol, and their magnitude is always positive or zero. Vectors add according to the triangle law or parallelogram law of addition. In two dimensions, a vector A can be resolved into rectangular components: A = Aₓ î + Aᵧ ĵ, where Aₓ = A cos θ, Aᵧ = A sin θ, and A = √(Aₓ² + Aᵧ²). Position vector r = x î + y ĵ gives velocity as v = dr/dt = vₓ î + vᵧ ĵ and acceleration as a = dv/dt = aₓ î + aᵧ ĵ. The direction of instantaneous velocity is always tangential to the path at that point. A projectile moves under constant downward acceleration due to gravity, with zero acceleration in the horizontal direction. Its trajectory is a parabola, and its horizontal and vertical motions take place independently. An object moving at constant speed along a circular path experiences centripetal acceleration directed radially inward toward the centre. The magnitude of this acceleration is a꜀ = v² / R = ω² R. Try each question first. Then tap it to see the answer. T = (2 v₀ sin θ₀) / g T = (2 × 20 × sin 30°) / 10 = (40 × 0.5) / 10 T = 20 / 10 = 2 s 2 s Rₘₐₓ = v₀² / g when projected at θ₀ = 45° Rₘₐₓ = (28)² / 9.8 = 784 / 9.8 Rₘₐₓ = 80 m 80 m a꜀ = v² / R a꜀ = (10)² / 5 = 100 / 5 a꜀ = 20 m s⁻² 20 m s⁻² Laws of Motion . Motion in a Straight Line . The 14 chapters of Class 11 Physics . CBSE does not give marks to one chapter. It prints 23 marks for Units I-III together (Physical World and Measurement; Kinematics; Laws of Motion). Motion in a Plane is part of that group. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Laws of Motion. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 3 NCERT book - 23 marks, Units I-III together - 3 quick checks - Assuming velocity is zero at the highest point of projectile motion . Only the vertical component of velocity (vᵧ) becomes zero at maximum height. The horizontal component remains non-zero and equals v₀ cos θ₀ throughout the flight. - Assuming acceleration in uniform circular motion is zero because speed is constant . Acceleration is non-zero because the direction of the velocity vector changes continuously. The inward centripetal acceleration has magnitude v² / R. - Adding vector magnitudes directly instead of using vector components . Two vectors can only be added algebraically after resolving them into components along common perpendicular axes, or by using R = √(A² + B² + 2 A B cos θ). ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 11](https://www.swavid.com/cbse/class-11) - [Physics](https://www.swavid.com/cbse/class-11/physics/chapters) - [Start free →](https://www.swavid.com/signup) - [All 14 chapters](https://www.swavid.com/cbse/class-11/physics/chapters) - [NCERT Physics Part I (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-11/physics/chapter/laws-of-motion) - [Open notes](https://www.swavid.com/cbse/class-11/physics/chapter/motion-in-a-straight-line) - [Class 11 Physics](https://www.swavid.com/cbse/class-11/physics/chapters) - [Start free →](https://www.swavid.com/signup)