Motion in
a Plane-
Class 11
By Dr. Umesh D. Patil
Rayat Shikshan Sanstha’s
Annasaheb Awate College,
Manchar
2.
Motion
Introduction to Motion
•Definition of Motion: A body is said to be in motion if it changes its position
with respect to time, relative to a reference point.
Motion
Change in position
over time
How to understand motion effectively?
Rest
No change in position
over time
3.
Planar
Motion
Motion confined
to atwo-
dimensional plane,
like a flat surface.
Spatial
Motion
Motion occurring
in three-
dimensional space,
allowing
movement in all
directions.
Rectilinear
Motion
Motion along a
straight line,
often seen in
simple linear
movements.
Understanding Motion
Types
4.
Acceleration
Vectors represent the
rateof change in
velocity.
Importance of Vectors in
Motion
Velocity
Vectors indicate the
speed and direction of
movement.
Displacement
Vectors show the
change in position of
an object.
5.
2. Rectilinear Motion
(Revision)
•Displacement vs. Distance:
• Distance: The total path length traveled by an object.
• Displacement: The shortest distance between the initial and final positions, with direction.
Calculate
Displaceme
nt
Shortest
distance with
direction
Determi
ne
Start/En
d
Identify initial
and final
positions
Displacement
Shortest distance
with direction
Distanc
e
Total path
length
traveled
Understanding otion:
𝒩 Distance & Displacement
6.
Average
Speed and
Velocity
Average Speed
Totaldistance divided by
total time taken.
Average Velocity
Total displacement divided
by total time taken.
Unveiling Average Speed and Velocity
7.
Instantaneous
Velocity
Velocity at a
specificinstant,
limit of average
velocity.
Instantaneous
Speed
Magnitude of
the
instantaneous
velocity, a scalar
quantity.
Instantaneous Velocity and
Speed
8.
•Acceleration: The rateof change of velocity with respect to time.
Acceleration is calculated
The Cycle of Acceleration
NewVelocity
Velocity Change
Velocity is updated
Velocity increases or
decreases
Acceleration
Occurs
Time Elapsed
Time passes during
velocity change
9.
The displacement ofa particle is given by s=4t2
+2t+1. Find the velocity at t=3s.
a) 26m/s b) 43m/s c) 36m/s d) 40m/s
10.
The velocity ofa particle is given by =3
𝑣 𝑡2
+2 +4. Find the acceleration at
𝑡
=2 .
𝑡
a) 32 m/s2
b) 20 m/s2
c) 14 m/s2
d) 40 m/s2
13.
v = u+ at
v2
= u2
+ 2as
Understanding Equations of Motion
s = ut + 1⁄2at2
Where:
• v = final velocity
• u = initial velocity
• a = acceleration
• t = time
• s = displacement
14.
A train startsfrom rest and accelerates uniformly at 2m/s2
. What will be its
velocity after 15 seconds?
a) 20m/s b) 15m/s c) 30m/s d) 60m/s
15.
A car acceleratesfrom rest at 3 m/s2
for 8 seconds. How far does it travel in this
time?
a) 96m b) 32m c) 64m d) 108m
16.
A vehicle movingwith a speed of 20m/s is brought to rest by applying brakes. If
the deceleration is 5 m/s2
, find the distance it travels before coming to rest.
a) 20m b) 40m c) 30m d) 60m
17.
Choose the appropriateframe of reference for velocity analysis.
Moving Frame
Provides relative velocity
Stationary Frame
Provides absolute velocity
• Vector Equation:
The position ofa particle is given by =3
𝑥 𝑡2
, =4 . Find the instantaneous
𝑦 𝑡
velocity vector at t=2s, and its magnitude.
a) 12 m/s b) 4 m/s c) 12.65 m/s d) 9.6 m/s
• Examples: Cricketball, basketball, bullet fired from a gun.
• Assumptions: Neglect air resistance, constant gravitational acceleration (g).
• Equations of Trajectory:
25.
A projectile isfired at u=50m/s at an angle θ=45∘
. What is the velocity at the
highest point?
a) 30.25 m/s b) 35.35 m/s c) 32.60 m/s d) 36.15 m/s
26.
Constant Speed
Object maintainsa steady speed
throughout the motion.
Cycle of Uniform Circular Motion
Object Moves in Circle
Object starts moving along a
circular path.
Repeat Motion
The cycle continues as the object
completes the
circle.
Changing Velocity
Velocity changes direction
continuously.
• Concept: Motion of an object along a circular path with constant speed.
Note that while the speed is constant, the velocity is constantly changing direction.
A 2 kgobject is moving in a circle of radius 4 meters at a speed of 3 m/s. What
is the centripetal force acting on the object?
a) 5 N b) 3 N c) 3.5 N d) 4.5 N
31.
A small ballof mass m=0.5kg is attached to a string of length ℓ=2 mℓ=2m. It
moves in a horizontal circle such that the string makes an angle =30 θ=30
𝜃 ∘ ∘
with the vertical. Find the speed of the ball.
a) 5 N b) 3 N c) 3.5 N d) 4.5 N