CLASS XI MAHARASHTRA STATE BOARD CHAPTER 3 MOTION IN A PLANE PHYSICS

1. Std : XI Year : 2021-22
Subject : PHYSICS
Chapter 3: Motion in a plane
CLASSXI
MAHARASHTRA STATE BOARD

2. CAN YOU RECALL?
1. What is meant by motion?
MOTION
“Motion is the phenomenon in which an object changes its
position over time.”
It is described by
• displacement, distance
• velocity, speed
• acceleration
• time
Types of
motion
Rotational
motion
Oscillatory
motion
Linear
motion
Reciprocating

3. CAN YOU RECALL?
2. What is rectilinear motion?

4. CAN YOU RECALL?
3. What is the difference between displacement and distance
travelled?

5. CAN YOU RECALL?
4. What is the difference between uniform and non-uniform
motion?

6. 3.1 INTRODUCTION
The motion of objects can be divided in three
categories:
(1) motion along a straight line, i.e., rectilinear
motion,
(2) motion in two dimensions, i.e., motion in a
plane and,
(3) motion in three dimensions, i.e., motion in
space.

7. 3.3 Motion in Two Dimensions - Motion in a Plane
if a particle travels along a circle and comes back to its original position, its
displacement will be zero but the path length will be equal to the
circumference of the circle.
3.3.1 Average and Instantaneous Velocities:

8. 3.3 Motion in Two Dimensions - Motion in a Plane
3.3.1 Average and Instantaneous Velocities:
Fig. (a) Motion in two dimensions
Fig. (b) Instantaneous velocity

9. 3.3 Motion in Two Dimensions - Motion in a Plane
3.3.2 Average and Instantaneous Acceleration:

11. 3.3 Motion in Two Dimensions - Motion in a Plane
3.3.3 Equations of Motion for an Object travelling a Plane with Uniform
Acceleration:

12. 3.3 Motion in Two Dimensions - Motion in a Plane
3.3.4 Relative Velocity
Example 3.4, 3.5, 3.6 - HOMEWORK

13. 3.3 Motion in Two Dimensions - Motion in a Plane
3.3.5 Projectile Motion
Any object in flight after being thrown with some velocity is called a projectile and its
motion is called projectile motion.
Fig.: Trajectory of a projectile.
At the highest point P,

14. 3.3 Motion in Two Dimensions - Motion in a Plane
3.3.5 Projectile Motion
Fig.: Trajectory of a projectile.
This maximum horizontal distance travelled by
the projectile is called the horizontal range R of
the projectile and depends on the magnitude
and direction of initial velocity of the projectile
as well as the value of acceleration due to gravity
at that place.

15. 3.3 Motion in Two Dimensions - Motion in a Plane
3.3.5 Projectile Motion
Fig.: Trajectory of a projectile.
Equation of motion for a projectile

16. 3.4 Uniform Circular Motion:
An object moving with constant speed along a circular path is said to be in
uniform circular motion (UCM).
In order to achieve both these requirements,
the acceleration must be
(i) perpendicular to the tangential velocity,
(ii) of constant magnitude and
(iii) always directed towards the centre of the
circular trajectory.
Thus, in order to realize a circular motion, there
are two requirements;
(i) tangential velocity and
(ii) centripetal force of suitable constant
magnitude.

17. 3.4 Uniform Circular Motion:
3.4.1 Period, Radius Vector and Angular Speed:
During one complete revolution, the angle described is
2S and the time taken is period T. Hence, the angular
speed
The unit of 𝜔 is radians/sec.

18. 3.4 Uniform Circular Motion:
3.4.2 Expression for Centripetal Acceleration:

19. 3.4 Uniform Circular Motion:
Conical pendulum
If the mass instead revolves in a horizontal circle and the string which makes a constant
angle with the vertical describes a cone whose vertex is the fixed point O, then mass
string system is called a conical pendulum.

20. Thank You