Speed — JEE Main Physics MCQs with Solutions
Free JEE Main Physics Speed MCQs with step-by-step solutions (36 questions). Part of Motion in 1 Dimension. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Speed · easy · theory
Speed is a
A. Scalar quantity ✓ Correct
B. Dimensionless number
C. Force
D. Vector quantity
Solution: Speed is the magnitude of how fast a body moves — no direction, hence scalar.
Q2 — Speed · easy · theory
Average speed is defined as
A. Total distance ÷ total time ✓ Correct
B. Change in velocity ÷ time
C. Distance × time
D. Total displacement ÷ total time
Solution: Average speed uses the full path length, not displacement.
Q3 — Speed · easy · theory
A car covers $60$ km in $1.5$ hours. Its average speed is
A. $90$ km/h
B. $60$ km/h
C. $30$ km/h
D. $40$ km/h ✓ Correct
Solution: $\frac{60}{1.5} = 40$ km/h.
Q4 — Speed · medium · theory
A body covers the first half of a distance at speed $v_1$ and the second half at $v_2$. Its average speed is
A. $\sqrt{v_1v_2}$
B. $\frac{v_1v_2}{v_1+v_2}$
C. $\frac{2v_1v_2}{v_1+v_2}$ ✓ Correct
D. $\frac{v_1+v_2}{2}$
Solution: Equal DISTANCES give the harmonic mean: $\bar v = \frac{2v_1v_2}{v_1+v_2}$. (A JEE favourite.)
Q5 — Speed · easy · theory
A car travels half the distance at $40$ km/h and the other half at $60$ km/h. Its average speed is
A. $45$ km/h
B. $48$ km/h ✓ Correct
C. $52$ km/h
D. $50$ km/h
Solution: $\bar v = \frac{2\times40\times60}{40+60} = \frac{4800}{100} = 48$ km/h — NOT $50$.
Q6 — Speed · easy · theory
A body moves at $v_1$ for half the TIME and $v_2$ for the other half. Its average speed is
A. $v_1+v_2$
B. $\frac{v_1+v_2}{2}$ ✓ Correct
C. $\sqrt{v_1v_2}$
D. $\frac{2v_1v_2}{v_1+v_2}$
Solution: Equal TIMES give the simple arithmetic mean.
Q7 — Speed · easy · theory
A car moves at $40$ km/h for $1$ hour and then $60$ km/h for $1$ hour. Its average speed is
A. $45$ km/h
B. $48$ km/h
C. $52$ km/h
D. $50$ km/h ✓ Correct
Solution: Equal times: $\bar v = \frac{40+60}{2} = 50$ km/h.
Q8 — Speed · easy · numerical
$72$ km/h expressed in m/s is
A. $20$ m/s ✓ Correct
B. $7.2$ m/s
C. $36$ m/s
D. $72$ m/s
Solution: Multiply by $\frac{5}{18}$: $72\times\frac{5}{18} = 20$ m/s.
Q9 — Speed · easy · theory
The speedometer of a car indicates
A. Instantaneous velocity
B. Instantaneous speed ✓ Correct
C. Average speed
D. Distance
Solution: It shows how fast the car is moving at that moment (no direction).
Q10 — Speed · easy · theory
The speed of a moving particle
A. Equals displacement/time
B. Can never be negative ✓ Correct
C. Can be negative
D. Is a vector
Solution: Speed is a magnitude; the smallest possible value is zero.
Q11 — Speed · easy · theory
In uniform circular motion, which remains constant?
A. Speed ✓ Correct
B. Displacement
C. Acceleration (as a vector)
D. Velocity
Solution: Speed stays the same while velocity continuously changes direction.
Q12 — Speed · easy · theory
A car goes to a town at $60$ km/h and returns by the same road at $30$ km/h. Its average speed for the whole trip is
A. $40$ km/h ✓ Correct
B. $90$ km/h
C. $45$ km/h
D. $50$ km/h
Solution: Equal distances: $\frac{2\times60\times30}{60+30} = 40$ km/h.
Q13 — Speed · easy · numerical
A sprinter runs $100$ m in $10$ s. His average speed is
A. $10$ m/s ✓ Correct
B. $100$ m/s
C. $5$ m/s
D. $36$ m/s
Solution: $\frac{100}{10} = 10$ m/s ($= 36$ km/h).
Q14 — Speed · medium · theory
At any instant, the instantaneous speed equals
A. The distance travelled
B. Zero
C. The average velocity
D. The magnitude of the instantaneous velocity ✓ Correct
Solution: Instant by instant, speed $= |\vec v|$ — they differ only over intervals with direction change.
Q15 — Speed · easy · theory
To convert km/h into m/s, multiply by
A. $3.6$
B. $\frac{1}{60}$
C. $\frac{5}{18}$ ✓ Correct
D. $\frac{18}{5}$
Solution: $1$ km/h $= \frac{1000}{3600}$ m/s $= \frac{5}{18}$ m/s.
Q16 — Speed · easy · theory
A car covers $200$ km in $2$ h, then $100$ km in another $2$ h. Its average speed over the journey is
A. $75$ km/h ✓ Correct
B. $100$ km/h
C. $50$ km/h
D. $150$ km/h
Solution: $\bar v = \frac{200+100}{2+2} = 75$ km/h.
Q17 — Speed · easy · theory
For any moving body, the average speed is
A. Less than the average velocity
B. Greater than or equal to the magnitude of average velocity ✓ Correct
C. Unrelated to average velocity
D. Always equal to average velocity
Solution: Distance $\geq |$displacement$|$, so dividing by the same time keeps the inequality.
Q18 — Speed · easy · theory
Thunder is heard $3$ s after a lightning flash. If sound travels at $330$ m/s, the storm is about
A. $110$ m away
B. $3.3$ km away
C. $330$ m away
D. $1$ km away ✓ Correct
Solution: Distance $= 330\times3 = 990$ m $\approx 1$ km (light arrives almost instantly).
Q19 — Speed · easy · numerical
A $100$ m long train crosses an electric pole in $5$ s. Its speed is
A. $25$ m/s
B. $5$ m/s
C. $20$ m/s ✓ Correct
D. $10$ m/s
Solution: To pass a point it must cover its own length: $\frac{100}{5} = 20$ m/s.
Q20 — Speed · medium · numerical
A $100$ m long train crosses a $400$ m long platform in $25$ s. Its speed is
A. $4$ m/s
B. $20$ m/s ✓ Correct
C. $25$ m/s
D. $16$ m/s
Solution: It must cover platform + its own length: $\frac{100+400}{25} = 20$ m/s. (Classic trap: not $400/25$.)
Q21 — Speed · easy · numerical
The speed of light in vacuum is approximately
A. $3\times10^{10}$ m/s
B. $3\times10^6$ m/s
C. $3\times10^8$ m/s ✓ Correct
D. $330$ m/s
Solution: $c \approx 3\times10^8$ m/s.
Q22 — Speed · easy · numerical
Walking at $4$ km/h, the time needed to cover $2$ km is
A. $60$ min
B. $15$ min
C. $8$ min
D. $30$ min ✓ Correct
Solution: $t = \frac{2}{4} = 0.5$ h $= 30$ minutes.
Q23 — Speed · medium · theory
A body covers one-third of a distance at $v$ and the remaining two-thirds at $2v$. Its average speed is
A. $2v$
B. $\frac{4v}{3}$
C. $\frac{5v}{3}$
D. $\frac{3v}{2}$ ✓ Correct
Solution: $t_1 = \frac{d}{3v}$, $t_2 = \frac{2d/3}{2v} = \frac{d}{3v}$; $\bar v = \frac{d}{2d/(3v)} = \frac{3v}{2}$.
Q24 — Speed · easy · numerical
A cyclist completes $3$ laps of a $400$ m track in $5$ minutes. The average speed is
A. Zero
B. $12$ m/s
C. $4$ m/s ✓ Correct
D. $2$ m/s
Solution: $\bar v = \frac{3\times400}{300} = 4$ m/s. (Average VELOCITY is zero — closed laps.)
Q25 — Speed · easy · numerical
A bullet travels at $720$ km/h. In m/s this is
A. $200$ m/s ✓ Correct
B. $72$ m/s
C. $2000$ m/s
D. $120$ m/s
Solution: $720\times\frac{5}{18} = 200$ m/s.
Q26 — Speed · easy · theory
If the speed of a body is constant, its velocity
A. Must be constant
B. Must be zero
C. Must increase
D. May still change (direction can change) ✓ Correct
Solution: Example: uniform circular motion — constant speed, continuously changing velocity.
Q27 — Speed · easy · theory
A car covers $30$ km at $20$ km/h and the next $30$ km at $30$ km/h. Its average speed is
A. $24$ km/h ✓ Correct
B. $25$ km/h
C. $26$ km/h
D. $22$ km/h
Solution: Equal distances: $\frac{2\times20\times30}{50} = 24$ km/h.
Q28 — Speed · medium · theory
Two cars move in the same direction at $80$ km/h and $50$ km/h. The speed of one relative to the other is
A. $130$ km/h
B. $80$ km/h
C. $30$ km/h ✓ Correct
D. $65$ km/h
Solution: Same direction: relative speed $= 80 - 50 = 30$ km/h.
Q29 — Speed · easy · theory
The dimensional formula of speed is
A. $[LT^{-1}]$ ✓ Correct
B. $[L]$
C. $[LT^{-2}]$
D. $[MLT^{-1}]$
Solution: Speed $=$ length/time $\Rightarrow [LT^{-1}]$.
Q30 — Speed · easy · theory
Over any time interval, if the average speed is zero then
A. The body returned to its start
B. The body moved uniformly
C. The body remained at rest for the whole interval ✓ Correct
D. The displacement was negative
Solution: Zero average speed means zero DISTANCE — impossible unless the body never moved at all.