Measurement of Length and Motion Part 4: MCQs (Q76–Q100)
Part 4 — Questions 76–100 (Problem-solving, reasoning, mixed revision)
76. An object covers equal distances in equal intervals of time. Its motion is called
A. Uniform acceleration
B. Uniform motion ← Correct answer: B
C. Non-uniform motion
D. Random motion
Explanations:
A) Acceleration involves changing velocity.
B) Correct — equal distances in equal times indicate uniform motion.
C/D) Incorrect.
77. A man walks at 5 km/h for 2 hours and then at 3 km/h for 3 hours. The total distance covered is
A. 10 km + 9 km = 19 km ⇒ Correct ← Correct answer: A
B. 5 km only
C. 15 km only
D. 30 km only
Explanations:
A) Correct — distance = 5×2 + 3×3 =10 +9 =19 km.
B/C/D) Incorrect.
78. If a car starts from rest and moves with constant acceleration 4 m/s², the speed after 5 s is
A. 4 m/s
B. 20 m/s ← Correct answer: B
C. 9 m/s
D. 1.25 m/s
Explanations:
A) (4×1) wrong time.
B) Correct — v = u + at = 0 + 4×5 = 20 m/s.
C/D) Incorrect.
79. A person walks 1 km east then 1 km north then 1 km west. His displacement from starting point is
A. 3 km
B. 1 km north ← Correct answer: B
C. 0 km
D. 1 km east
Explanations:
A) Sum of distances.
B) Correct — east and west cancel, net displacement = 1 km north.
C/D) Incorrect.
80. A bus moves from A to B (30 km), then from B to C (40 km) in 1 hour each. Its average speed for entire journey is
A. 70 km/h
B. (Total distance 70 km) / (total time 2 h) = 35 km/h ← Correct answer: B
C. 140 km/h
D. 70 km only
Explanations:
A/C/D) Wrong calculations.
B) Correct — average speed = total distance / total time = 70/2 = 35 km/h.
81. On a distance-time graph a curved line that becomes steeper with time indicates
A. Decreasing speed
B. Increasing speed (accelerating) ← Correct answer: B
C. Resting object
D. Negative time
Explanations:
A/C/D) Incorrect.
B) Correct — steeper slope = higher speed, curve steepening means acceleration.
82. Which of the following can change velocity of an object?
A. Change in speed only
B. Change in direction only
C. Either change in magnitude (speed) or direction or both ← Correct answer: C
D. None of the above
Explanations:
A/B) Partial truths.
C) Correct — velocity changes if speed or direction changes.
83. Two cars start from same point. Car A travels east 30 km in 0.5 h; Car B travels north 40 km in 0.5 h. Which car has greater average speed?
A. Car A (60 km/h)
B. Car B (80 km/h)
C. Car B ← Correct answer: B
D. Both same
Explanations:
A) Car A speed = 30/0.5 = 60 km/h.
B) Car B speed = 40/0.5 = 80 km/h (greater).
C) Correct — B has greater speed.
D) Incorrect.
84. A sprinter runs 100 m in 10 s. His average speed and average velocity (assuming straight line) are
A. 10 m/s, 10 m/s (same) ⇒ Correct ← Correct answer: A
B. 10 m/s, 0 m/s
C. 0 m/s, 10 m/s
D. 1000 m/s, 1000 m/s
Explanations:
A) Correct — average speed = 100/10 =10 m/s; if displacement =100 m in same direction then average velocity = 10 m/s.
B/C/D) Incorrect.
85. A distance-time graph of a moving object is a straight line passing through origin with slope 4. Units of slope are m/s. What does slope represent?
A. Acceleration only
B. Speed = 4 m/s ← Correct answer: B
C. Mass
D. Temperature
Explanations:
A) Slope of v-t graph gives acceleration; here slope of d-t graph is speed.
B) Correct — slope = Δdistance/Δtime = speed.
C/D) Irrelevant.
86. A car travels at 72 km/h. Convert this speed into m/s. (1 km = 1000 m, 1 h = 3600 s)
A. 20 m/s ⇒ Correct ← Correct answer: A
B. 200 m/s
C. 2 m/s
D. 0.2 m/s
Explanations:
A) Correct — 72×1000/3600 = 20 m/s.
B/C/D) Incorrect.
87. A runner goes around a circular track and returns to start in 50 s. If track circumference is 400 m, his average speed and average velocity are
A. 8 m/s, 0 m/s ⇒ Correct ← Correct answer: A
B. 8 m/s, 8 m/s
C. 0 m/s, 8 m/s
D. 400 m/s, 50 m/s
Explanations:
A) Correct — speed = 400/50 = 8 m/s; displacement = 0 so average velocity =0.
B/C/D) Wrong.
88. Which of the following describes instantaneous acceleration?
A. Change in velocity over a long time only
B. Rate of change of velocity at an instant (limit of average acceleration as time→0) ← Correct answer: B
C. Velocity squared
D. Temperature over time
Explanations:
A/C/D) Incorrect definitions.
B) Correct — instantaneous acceleration is derivative of velocity.
89. A ball thrown straight up has acceleration (neglecting air resistance)
A. Upwards constant g
B. Downwards equal to g (≈9.8 m/s²) ← Correct answer: B
C. Zero at top only
D. Increasing in upwards direction
Explanations:
A) Direction reversed — g downwards.
B) Correct — gravity causes constant downwards acceleration.
C) Velocity zero at top but acceleration still g downwards.
D) Incorrect.
90. Average velocity formula is useful when motion includes changes of speed/direction. It equals
A. Total time / total distance
B. Total displacement / total time ← Correct answer: B
C. Distance × time
D. Acceleration / time
Explanations:
A/C/D) Wrong formula.
B) Correct.
91. A car moves 60 m east in 3 s; its average velocity is
A. 20 m/s east ⇒ Correct ← Correct answer: A
B. 180 m/s east
C. 0 m/s
D. 20 s/m
Explanations:
A) Correct — 60/3 = 20 m/s east.
B/C/D) Incorrect.
92. On a velocity-time graph, zero slope indicates
A. Acceleration is zero ⇒ Correct ← Correct answer: A
B. Speed is infinity
C. Distance negative
D. Time reversal
Explanations:
A) Correct — slope = acceleration; zero slope => zero acceleration (constant velocity).
B/C/D) Incorrect.
93. Which factor does NOT affect average speed?
A. Total distance covered
B. Colour of the vehicle ← Correct answer: B
C. Total time taken
D. Stops/rests included in time
Explanations:
A/C/D) Affect average speed.
B) Correct — colour irrelevant.
94. A car starts at 0, accelerates uniformly to 30 m/s in 15 s. Its average speed during acceleration is
A. 30 m/s
B. (0 +30)/2 =15 m/s ← Correct answer: B
C. 10 m/s
D. 45 m/s
Explanations:
A) Final speed not average.
B) Correct — for uniform acceleration from u to v average speed = (u+v)/2 =15 m/s.
C/D) Incorrect.
95. An object with zero velocity always has zero acceleration. True or False?
A. True always
B. False (object at rest may have non-zero acceleration if instantaneous velocity changes) ← Correct answer: B
C. True only at night
D. Cannot say
Explanations:
A) Not always — e.g., object momentarily at rest in oscillation has non-zero acceleration.
B) Correct — zero velocity doesn’t guarantee zero acceleration.
C/D) Nonsense.
96. Light-year is a unit of
A. Time only
B. Distance (distance light travels in one year) ← Correct answer: B
C. Mass only
D. Temperature
Explanations:
A/C/D) Wrong.
B) Correct — astronomical distance unit.
97. If displacement is proportional to square of time (x ∝ t²), the motion indicates
A. Uniform velocity
B. Uniform acceleration (constant) ← Correct answer: B
C. No motion
D. Negative displacement always
Explanations:
A) Linear relation x ∝ t.
B) Correct — x = ut + 1/2 at² with u=0 gives x ∝ t² for constant acceleration.
C/D) Incorrect.
98. A particle moves so that v = 3t (m/s). Distance covered in first 4 s is
A. 24 m
B. ∫ from 0 to 4 of 3t dt = (3/2) t² |0..4 = (3/2)×16 =24 m ← Correct answer: B
C. 48 m
D. 12 m
Explanations:
A/B) Both indicate same; B shows method.
C/D) Wrong.
99. A person cycles to school 2 km away and returns immediately home. The total distance and displacement are
A. 4 km, 0 km ⇒ Correct ← Correct answer: A
B. 0 km, 4 km
C. 2 km, 2 km
D. 1 km, 1 km
Explanations:
A) Correct — go and return total =4 km, net displacement =0.
B/C/D) Incorrect.
100. Final quick revision — Which statement is MOST accurate?
A. Distance and displacement are identical in all cases
B. Distance is scalar, displacement is vector; average speed = total distance/total time; average velocity = displacement/time ← Correct answer: B
C. Speed has direction always
D. Motion cannot be measured
Explanations:
A/C/D) Incorrect.
B) Correct — concise summary tying together key concepts from the chapter.