📘 Chapter 8 – Motion - educationlearners.shop

📘 Chapter 8 – Motion

🧠 Easy Notes

🔹 1. What is Motion?

When the position of an object changes with time, it is said to be in motion.
Types of motion: Rectilinear (straight line), Circular, Periodic.

🔹 2. Distance and Displacement

Distance: Total path covered (scalar quantity).
Displacement: Shortest distance between initial and final position (vector quantity).
📝 Distance ≥ Displacement

🔹 3. Speed and Velocity

Term	Formula	Type
Speed	Distance / Time	Scalar
Velocity	Displacement / Time	Vector
Uniform Speed	Equal distances in equal time	—
Variable Speed	Unequal distances in equal time	—

🔹 4. Acceleration

Rate of change of velocity.
📌 Formula:
Acceleration (a) = (Final velocity - Initial velocity) / Time
📌 Unit: m/s²

🔹 5. Graphs of Motion

a) Distance-Time Graph:

Straight line = uniform speed
Curved line = non-uniform speed

b) Velocity-Time Graph:

Slope = acceleration
Area under graph = distance

🔹 6. Equations of Uniform Acceleration

1️⃣ v = u + at
2️⃣ s = ut + ½at²
3️⃣ v² = u² + 2as
Where:

u = initial velocity
v = final velocity
a = acceleration
s = displacement
t = time

🔹 7. Uniform Circular Motion

When an object moves in a circle at constant speed.
Direction changes continuously, so it’s accelerated motion.

✅ MCQs

Motion in a straight line is:
a) Circular motion
b) Periodic motion
c) Rectilinear motion
d) Uniform motion
Distance is a:
a) Vector
b) Scalar
c) Force
d) Acceleration
SI unit of speed is:
a) m
b) m/s
c) m/s²
d) km/hr
If displacement is zero, then distance:
a) Is also zero
b) Must be zero
c) Can’t be zero
d) May or may not be zero
Rate of change of velocity is:
a) Speed
b) Force
c) Acceleration
d) Displacement
What does the slope of velocity-time graph show?
a) Distance
b) Speed
c) Acceleration
d) Displacement
What is the area under velocity-time graph?
a) Speed
b) Distance
c) Acceleration
d) Time
Which of the following is vector quantity?
a) Speed
b) Distance
c) Time
d) Displacement
If a car moves with uniform speed, acceleration is:
a) Zero
b) Constant
c) Infinite
d) Negative
If initial velocity is 0, and a = 2 m/s², t = 5 s, then final velocity is:
a) 5 m/s
b) 10 m/s
c) 20 m/s
d) 15 m/s
Which equation gives displacement?
a) v = u + at
b) s = ut + ½ at²
c) v² = u² + 2as
d) F = ma
Uniform circular motion is:
a) Static
b) Accelerated
c) Non-uniform
d) Variable
Displacement can be:
a) More than distance
b) Equal to distance
c) Less than distance
d) b or c
Which quantity has both magnitude and direction?
a) Scalar
b) Speed
c) Vector
d) Distance
SI unit of acceleration is:
a) m
b) m/s
c) m/s²
d) km/h

✅ Assertion & Reason

A: Acceleration is zero in uniform motion.
R: Speed changes in uniform motion.
a) A and R true, R explains A
b) A and R true, R doesn’t explain A
c) A true, R false
d) A false, R true

A: Displacement is always equal to or less than distance.
R: Displacement is the shortest path.
a) A and R true, R explains A
b) A and R true, R doesn’t explain A
c) A true, R false
d) A false, R true

A: Velocity is a scalar quantity.
R: It has only magnitude.
a) A and R true, R explains A
b) A and R true, R doesn’t explain A
c) A true, R false
d) A false, R true

A: In circular motion, speed is constant but velocity changes.
R: Direction of motion keeps changing.
a) A and R true, R explains A
b) A and R true, R doesn’t explain A
c) A true, R false
d) A false, R true

A: The slope of distance-time graph gives speed.
R: Speed = distance/time.
a) A and R true, R explains A
b) A and R true, R doesn’t explain A
c) A true, R false
d) A false, R true

✅ Case-Based Study

📘 Passage:
A bus starts from rest and moves with a uniform acceleration of 2 m/s² for 10 seconds. Then it continues at constant speed for 5 seconds. Finally, it slows down with a uniform retardation of 1 m/s² till it stops.

What is the acceleration during the first 10 seconds?
a) 0 m/s²
b) 2 m/s²
c) 1 m/s²
d) 10 m/s²
Final velocity after 10 seconds is:
a) 10 m/s
b) 20 m/s
c) 5 m/s
d) 15 m/s
Distance covered during acceleration phase:
a) 100 m
b) 50 m
c) 20 m
d) 150 m
During constant speed, distance covered in 5 s is:
a) 10 m
b) 50 m
c) 100 m
d) 25 m
Retardation value is:
a) +2 m/s²
b) -2 m/s²
c) -1 m/s²
d) 0

✅ Reason-Based Questions

Why is motion relative?
Because it depends on the observer’s frame of reference.
Why is displacement a vector?
Because it has both magnitude and direction.
Why can distance never be negative?
Because it’s a scalar and only measures magnitude.
Why is velocity different from speed?
Because velocity has direction, speed does not.
Why is area under velocity-time graph equal to distance?
Because area = velocity × time, which is equal to distance.
Why is circular motion accelerated?
Because direction changes, so velocity changes.
Why is acceleration zero in uniform speed?
Because there is no change in velocity.
Why do we prefer displacement for equations of motion?
Because it’s a vector and gives correct direction too.
Why do we use SI units?
To have a standard system worldwide.
Why can displacement be zero but distance not?
Because if start and end points are same, displacement is zero but distance is still covered.
Why do we need velocity-time graphs?
To calculate distance and understand motion.
Why is slope of distance-time graph speed?
Because slope = rise/run = distance/time = speed.
Why is v = u + at called first equation of motion?
Because it directly relates velocity, acceleration and time.
Why is second equation useful for distance?
Because it gives distance when initial velocity and acceleration are known.
Why do objects in circular motion have constant speed but changing velocity?
Because their direction changes continuously.

✅ Answer Key

MCQs:
1–c, 2–b, 3–b, 4–d, 5–c, 6–c, 7–b, 8–d, 9–a, 10–c, 11–b, 12–b, 13–d, 14–c, 15–c

Assertion & Reason:
16–c, 17–a, 18–d, 19–a, 20–a

Case-Based:
21–b, 22–b, 23–a, 24–b, 25–c