Chapter 3: Motion in a Plane

Physics Part-1 • Class 11

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Chapter Analysis

Intermediate11 pages • English

Quick Summary

The chapter 'Motion in a Plane' introduces motion in two-dimensional and three-dimensional spaces, employing vector mathematics to describe physical quantities such as displacement, velocity, and acceleration. It covers various topics, including vector operations, resolution of vectors, motion with constant acceleration, projectile motion, and uniform circular motion. Each concept is addressed with relevant mathematical formulations and graphical representations to aid comprehension.

Key Topics

  • Vectors and Scalars
  • Vector Addition and Subtraction
  • Resolution of Vectors
  • Projectile Motion
  • Uniform Circular Motion
  • Motion with Constant Acceleration
  • Graphical and Analytical Vector Methods

Learning Objectives

  • Distinguish between scalar and vector quantities.
  • Perform vector addition and subtraction using both graphical and analytical methods.
  • Resolve vectors into components and understand their utility in motion analysis.
  • Analyze motion in a plane, considering both constant acceleration and projectile motion.
  • Understand the characteristics and calculations associated with uniform circular motion.

Questions in Chapter

What is the magnitude and direction of vector A if Ax = 3 and Ay = 4?

Answer: The magnitude is 5 and the direction is 53.1 degrees from the x-axis.

Page 44

An insect trapped in a circular groove of radius 12 cm moves along the groove steadily and completes 7 revolutions in 100 s. What is the angular speed, and the linear speed of the motion?

Answer: The angular speed ω is 0.44 rad/s and the linear speed v is 5.3 cm/s.

Page 43

A cricket ball is thrown at a speed of 28 m/s in a direction 30° above the horizontal. Calculate the maximum height.

Answer: The maximum height is 10.0 m.

Page 41

Additional Practice Questions

Explain the concept of uniform circular motion.

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Answer: Uniform circular motion refers to motion in a circular path with constant speed. Although the speed is constant, the velocity is not because the direction continuously changes. The acceleration is directed towards the center of the circle and has a magnitude of v²/R, where v is the speed and R is the radius of the circular path.

How does projectile motion demonstrate independence of motion in perpendicular directions?

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Answer: Projectile motion is a combination of two independent motions: horizontal motion with uniform velocity and vertical motion with uniform acceleration due to gravity. These two components do not affect each other, allowing projectiles to follow a parabolic path.

Derive the equation for the range of a projectile.

hard

Answer: The range R of a projectile launched with initial velocity v₀ at an angle θ₀ is given by R = (v₀²/g) * sin(2θ₀). This formula is derived by eliminating the time variable from the x- and y-coordinate equations of motion, considering the horizontal motion covers the maximum distance when θ = 45°.

If a vector B has a magnitude of 10 and makes an angle of 60 degrees with the positive x-axis, find its components.

easy

Answer: The x-component of vector B is Bx = 10 cos 60° = 5, and the y-component is By = 10 sin 60° = 8.66.

What role do unit vectors play in vector operations?

easy

Answer: Unit vectors define direction and have a magnitude of one. They are used to express vectors in terms of their components, facilitating the process of vector addition, subtraction, and other operations. Notationally, unit vectors i, j, and k refer to the direction along the x, y, and z axes, respectively.