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Motion & Kinematics — Homi Bhabha Class 9 Physics MCQs with Solutions
Free Homi Bhabha Class 9 Physics Motion & Kinematics MCQs with step-by-step solutions covering Scalar & Vector Quantities, Distance & Displacement, Speed & Velocity, Acceleration, Equations of Motion. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — Scalar & Vector Quantities · easy · theory
Which one of the following is a vector quantity?
A. Mass
B. Distance
C. Speed
D. Displacement ✓ Correct
Solution: A vector needs both magnitude and direction. Displacement has a direction, while speed, distance and mass have magnitude only, so they are scalars.
Q2 — Distance & Displacement · easy · theory
The displacement of a moving body can be:
A. Always greater than the distance
B. Zero even when the distance is not zero ✓ Correct
C. Always positive
D. Never zero
Solution: If a body returns to its starting point, its displacement is zero although the distance travelled is not zero. Displacement can be positive, negative or zero.
Q3 — Speed & Velocity · easy · theory
The rate of change of distance with time is called:
A. Speed ✓ Correct
B. Displacement
C. Acceleration
D. Velocity
Solution: Speed is the distance travelled per unit time. Velocity, in contrast, is the displacement per unit time and is a vector.
Q4 — Acceleration · easy · theory
Acceleration is defined as the rate of change of:
A. Speed only
B. Velocity ✓ Correct
C. Displacement
D. Distance
Solution: Acceleration = change in velocity divided by time taken. Because velocity is a vector, acceleration is a vector too.
Q5 — Equations of Motion · easy · theory
For a body moving with uniform acceleration, which of these is the first equation of motion?
A. s = u t + 1/2 a t squared
B. v = u + a t ✓ Correct
C. v squared = u squared + 2 a s
D. s = v t
Solution: The first equation of motion links final velocity, initial velocity, acceleration and time: v = u + a t.
Q6 — Scalar & Vector Quantities · hard · numerical
Two forces of 3 N and 4 N act on a body at right angles to each other. The magnitude of their resultant is:
A. 5 N ✓ Correct
B. 1 N
C. 7 N
D. 12 N
Solution: For perpendicular vectors the resultant $= \sqrt{3^2 + 4^2} = \sqrt{25} = 5$ N (not the scalar sum 7 N).
Q7 — Scalar & Vector Quantities · hard · numerical
A boy walks 6 m towards the east and then 8 m towards the north. The magnitude of his net displacement is:
A. 14 m
B. 2 m
C. 48 m
D. 10 m ✓ Correct
Solution: Perpendicular displacements add as vectors: $\sqrt{6^2 + 8^2} = \sqrt{100} = 10$ m (14 m is the total distance).
Q8 — Distance & Displacement · hard · numerical
An athlete completes exactly one full round of a circular track of radius 7 m. His displacement is:
A. 0 m ✓ Correct
B. 7 m
C. 14 m
D. 44 m
Solution: After one complete round he returns to the start, so displacement is 0 (the distance covered is $2\pi r = 44$ m).
Q9 — Distance & Displacement · hard · numerical
A runner covers half a round of a circular track of diameter 14 m. His displacement is (take $\pi = 22/7$):
A. 44 m
B. 14 m ✓ Correct
C. 7 m
D. 22 m
Solution: Half a round ends at the diametrically opposite point, so displacement = diameter = 14 m (distance $= \pi r = 22$ m).
Q10 — Speed & Velocity · hard · numerical
A car covers the first half of a distance at 30 km/h and the second half at 60 km/h. Its average speed for the whole journey is:
A. 40 km/h ✓ Correct
B. 45 km/h
C. 50 km/h
D. 90 km/h
Solution: For equal distances, average speed $= \dfrac{2 \times 30 \times 60}{30 + 60} = 40$ km/h (45 km/h wrongly averages the speeds).
Q11 — Speed & Velocity · hard · theory
A body can have a constant speed but a changing velocity when it moves:
A. in a straight line at a steady rate
B. with increasing speed
C. and then stops
D. in a circular path at a steady rate ✓ Correct
Solution: In uniform circular motion the direction changes continuously, so velocity changes even though the speed is constant.
Q12 — Acceleration · hard · numerical
A car moving at 90 km/h is brought to rest in 5 s. Its retardation is:
A. 25 m/s²
B. 4.5 m/s²
C. 18 m/s²
D. 5 m/s² ✓ Correct
Solution: Convert: $90$ km/h $= 25$ m/s; retardation $= \dfrac{25}{5} = 5$ m/s² (18 m/s² comes from forgetting to convert km/h).
Q13 — Acceleration · hard · theory
Assertion (A): A body thrown vertically upward has zero velocity but non-zero acceleration at its highest point. Reason (R): At the highest point gravity still acts on the body.
A. A is true but R is false
B. A is false but R is true
C. Both A and R are true and R is the correct explanation of A ✓ Correct
D. Both A and R are true but R is NOT the correct explanation of A
Solution: At the top $v = 0$, but gravity ($g$) still acts downward, so acceleration is non-zero — R correctly explains A.
Q14 — Acceleration · hard · numerical
On a velocity–time graph, a straight line rises from 0 to 20 m/s in 4 s. The acceleration represented is:
A. 80 m/s²
B. 0.2 m/s²
C. 5 m/s² ✓ Correct
D. 4 m/s²
Solution: On a v–t graph, acceleration = slope $= \dfrac{20 - 0}{4} = 5$ m/s².
Q15 — Equations of Motion · hard · numerical
A body moving at 10 m/s accelerates uniformly at 2 m/s². The distance it covers in the next 3 s is:
A. 9 m
B. 30 m
C. 48 m
D. 39 m ✓ Correct
Solution: $s = ut + \tfrac12 a t^2 = (10)(3) + \tfrac12 (2)(9) = 30 + 9 = 39$ m.
Q16 — Equations of Motion · hard · numerical
A car moving at 20 m/s applies brakes producing a retardation of 5 m/s². The distance it travels before stopping is:
A. 40 m ✓ Correct
B. 80 m
C. 4 m
D. 20 m
Solution: $v^2 = u^2 - 2as \Rightarrow 0 = 400 - 2(5)s \Rightarrow s = \dfrac{400}{10} = 40$ m.
Q17 — Equations of Motion · hard · numerical
The stopping distance of a vehicle (for the same braking force) is proportional to the square of its speed. If the speed is doubled, the stopping distance becomes:
A. 4 times ✓ Correct
B. unchanged
C. 8 times
D. 2 times
Solution: Since $s \propto v^2$, doubling $v$ multiplies the stopping distance by $2^2 = 4$.
Q18 — Scalar & Vector Quantities · hard · numerical
Two vectors of magnitudes 3 units and 4 units act at a single point. Which of the following can NOT be the magnitude of their resultant?
A. 1 unit
B. 5 units
C. 8 units ✓ Correct
D. 7 units
Solution: The resultant of two vectors lies between the difference and the sum of their magnitudes, that is from 4 minus 3 = 1 unit to 4 plus 3 = 7 units. So 1 to 7 are possible, but 8 units is not.
Q19 — Distance & Displacement · hard · numerical
A car travels 6 km north, then 8 km east, then 6 km south. What is the magnitude of its displacement from the start?
A. 14 km
B. 20 km
C. 8 km ✓ Correct
D. 10 km
Solution: The 6 km north and 6 km south cancel out, leaving only 8 km east. So the displacement is 8 km. The total distance travelled is 20 km, which is the common wrong answer.
Q20 — Speed & Velocity · hard · numerical
A car covers the first half of a journey at 40 km/h and the second half of equal distance at 60 km/h. What is its average speed for the whole journey?
A. 48 km/h ✓ Correct
B. 50 km/h
C. 100 km/h
D. 24 km/h
Solution: For two equal distances the average speed is the harmonic mean = (2 x 40 x 60) divided by (40 + 60) = 4800 divided by 100 = 48 km/h. The simple average of 50 km/h is the common mistake because more time is spent at the slower speed.
Q21 — Speed & Velocity · hard · theory
Assertion (A): A body can have constant speed and yet a changing velocity. Reason (R): Velocity is a vector, so a change of direction changes the velocity even if the magnitude stays the same. Choose the correct option.
A. Both A and R are true but R is not the correct explanation of A
B. Both A and R are true and R is the correct explanation of A ✓ Correct
C. A is true but R is false
D. A is false but R is true
Solution: A body in uniform circular motion moves at constant speed but its direction changes at every instant, so its velocity changes. This happens precisely because velocity is a vector, so R correctly explains A.
Q22 — Acceleration · hard · theory
A ball is thrown vertically upward. At the highest point of its path, which statement is correct?
A. Both its velocity and acceleration are zero
B. Both velocity and acceleration point upward
C. Its velocity is zero but its acceleration is not zero ✓ Correct
D. Its acceleration is zero but its velocity is not zero
Solution: At the top the ball stops for an instant, so its velocity is zero. But gravity still acts, so the acceleration is g pointing downward, about 9.8 m/s squared. It never becomes zero during the flight.
Q23 — Equations of Motion · hard · numerical
A car moving at 20 m/s is brought to rest over a distance of 50 m by uniform braking. What is the magnitude of its retardation?
A. 10 m/s squared
B. 2 m/s squared
C. 8 m/s squared
D. 4 m/s squared ✓ Correct
Solution: Using v squared = u squared + 2 a s: 0 = 20 squared + 2 x a x 50, so 0 = 400 + 100 a, giving a = minus 4 m/s squared. The magnitude of the retardation is 4 m/s squared.
Q24 — Equations of Motion · hard · numerical
A stone is dropped from rest from a height. Taking g = 10 m/s squared, how far does it fall during the first 3 seconds?
A. 45 m ✓ Correct
B. 90 m
C. 15 m
D. 30 m
Solution: Using s = u t + 1/2 g t squared with u = 0: s = 1/2 x 10 x 3 squared = 1/2 x 10 x 9 = 45 m.
Q25 — Scalar & Vector Quantities · medium · theory
Which of the following groups contains ONLY vector quantities?
A. Displacement, velocity, acceleration, force ✓ Correct
B. Distance, speed, mass, time
C. Displacement, speed, energy, force
D. Speed, velocity, distance, force
Solution: Vectors need magnitude AND direction: displacement, velocity, acceleration and force qualify; distance, speed, mass, time and energy are scalars.
Q26 — Scalar & Vector Quantities · medium · theory
Assertion (A): The distance covered by a body can never be negative. Reason (R): Distance is a scalar quantity that only has magnitude.
A. A is true but R is false
B. A is false but R is true
C. Both A and R are true but R is NOT the correct explanation of A
D. Both A and R are true and R is the correct explanation of A ✓ Correct
Solution: Distance is a scalar (magnitude only), so it is always positive or zero — R correctly explains A.
Q27 — Scalar & Vector Quantities · medium · theory
A quantity that depends only on the initial and final positions of a body, and not on the path taken, is:
A. Speed
B. Displacement ✓ Correct
C. Total path length
D. Distance
Solution: Displacement is the straight line from start to finish; it is path-independent, unlike distance.
Q28 — Scalar & Vector Quantities · medium · theory
Which one of the following is a scalar quantity?
A. Speed ✓ Correct
B. Velocity
C. Displacement
D. Acceleration
Solution: Speed has magnitude only, so it is a scalar; velocity, displacement and acceleration are vectors.
Q29 — Distance & Displacement · medium · numerical
A body moves 4 m towards the north and then 3 m towards the east. The distance and displacement respectively are:
A. 1 m and 5 m
B. 7 m and 5 m ✓ Correct
C. 7 m and 7 m
D. 5 m and 7 m
Solution: Distance $= 4 + 3 = 7$ m; displacement $= \sqrt{4^2 + 3^2} = 5$ m.
Q30 — Distance & Displacement · medium · numerical
A car travels 5 km due east and then returns 5 km due west to its starting point. Its total distance and displacement are:
A. 0 km and 10 km
B. 10 km and 10 km
C. 10 km and 0 km ✓ Correct
D. 5 km and 5 km
Solution: Distance is the whole path $= 10$ km; since it returns to start, displacement $= 0$.