Class 9 Science Chapter 9 Motion and Time MCQ with Answers (30 Solved Questions)

The rationalised 2024-25 CBSE syllabus emphasises conceptual understanding and quick problem-solving—precisely what MCQs test. Unlike descriptive questions, MCQs force you to eliminate wrong options, a skill that sharpens your subject mastery in 30 seconds. In Motion and Time, MCQs commonly target: (1) Identifying whether motion is uniform or non-uniform from a description or graph; (2) Calculating speed or distance using distance = speed × time; (3) Reading and interpreting distance-time graphs to find average speed; (4) Understanding the time period of a simple pendulum and its dependence on length (T = 2π√(L/g)); (5) Applying the concept of relative motion. MCQs also appear in Class 9 Science Olympiads, entrance exams like JEE/NEET preparation, and board practicals. Scoring 95+ on Motion and Time MCQs requires: (a) knowing all formulas by heart, (b) recognising trap options (common misconceptions), and (c) managing time—typically 1 minute per question. This guide trains all three skills with real-world numericals and graph-reading scenarios.

These questions test recall of definitions and straightforward application of formulas. **Q1.** Speed is a _____ quantity because it has only magnitude, not direction. (A) vector (B) scalar (C) composite (D) relative **Answer:** (B) scalar **Reason:** Speed = distance / time (a ratio of scalar quantities); velocity is the vector form because it includes direction. **Q2.** An object travels 120 m in 5 seconds. Its speed is: (A) 24 m/s (B) 600 m/s (C) 25 m/s (D) 0.04 m/s **Answer:** (A) 24 m/s **Reason:** Speed = 120 ÷ 5 = 24 m/s. **Q3.** Which of the following is an example of uniform motion? (A) A car moving on a busy road (B) A train moving at a constant speed on a straight track (C) A ball rolling down a slope (D) A person walking in a crowded marketplace **Answer:** (B) A train moving at a constant speed on a straight track **Reason:** Uniform motion means equal distances in equal time intervals; only option B guarantees this. **Q4.** A distance-time graph showing a _____ line indicates uniform motion. (A) curved (B) straight (C) vertical (D) horizontal **Answer:** (B) straight **Reason:** Constant slope on a distance-time graph = constant speed = uniform motion. **Q5.** The time period of a simple pendulum depends on: (A) mass of the bob (B) length of the string (C) colour of the bob (D) amplitude of swing **Answer:** (B) length of the string **Reason:** T = 2π√(L/g); time period depends only on length L and acceleration due to gravity g, not mass. **Q6.** If a pendulum completes 20 oscillations in 40 seconds, its time period is: (A) 2 seconds (B) 0.5 seconds (C) 800 seconds (D) 20 seconds **Answer:** (A) 2 seconds **Reason:** Time period = Total time ÷ Number of oscillations = 40 ÷ 20 = 2 s. **Q7.** Non-uniform motion is characterized by: (A) constant speed (B) equal distances in equal time intervals (C) unequal distances in equal time intervals (D) zero acceleration **Answer:** (C) unequal distances in equal time intervals **Reason:** Non-uniform motion has changing speed; distance covered varies from interval to interval. **Q8.** An object moves 50 m north, then 30 m south. Total distance and displacement are: (A) Distance = 80 m, Displacement = 20 m south (B) Distance = 20 m, Displacement = 80 m (C) Distance = 50 m, Displacement = 30 m (D) Distance = 30 m, Displacement = 50 m **Answer:** (A) Distance = 80 m, Displacement = 20 m south **Reason:** Distance = 50 + 30 = 80 m (total path); Displacement = |50 − 30| = 20 m in the north direction (net change). **Q9.** Average speed is calculated as: (A) Total distance ÷ Total time (B) Total displacement ÷ Total time (C) Instantaneous distance ÷ Time (D) Change in velocity ÷ Time **Answer:** (A) Total distance ÷ Total time **Reason:** Average speed considers the entire path length, not just final position. **Q10.** A car travels at 60 km/h for 2 hours. Distance covered is: (A) 30 km (B) 120 km (C) 62 km (D) 58 km **Answer:** (B) 120 km **Reason:** Distance = Speed × Time = 60 × 2 = 120 km.

These questions require interpreting graphs, comparing scenarios, or applying formulas in multi-step contexts. **Q11.** A distance-time graph shows a horizontal line at 50 m from t = 0 to t = 5 s. This means: (A) The object is moving at constant speed (B) The object is at rest 50 m away from origin (C) The object accelerates uniformly (D) The object moves 50 m every second **Answer:** (B) The object is at rest 50 m away from origin **Reason:** Horizontal line = no change in distance = zero velocity = object is stationary at that position. **Q12.** Two cyclists travel the same 100 m distance. Cyclist A takes 5 seconds, Cyclist B takes 8 seconds. Their speeds are in the ratio: (A) 5:8 (B) 8:5 (C) 100:100 (D) 20:12.5 or 8:5 **Answer:** (D) 20:12.5 or 8:5 **Reason:** Speed A = 100/5 = 20 m/s; Speed B = 100/8 = 12.5 m/s; Ratio = 20:12.5 = 8:5. **Q13.** A car accelerates from rest and its speed increases from 0 to 40 m/s in 8 seconds. A distance-time graph for this motion would show: (A) a straight horizontal line (B) a straight diagonal line from origin (C) a curved line (concave upward) (D) a curved line (concave downward) **Answer:** (C) a curved line (concave upward) **Reason:** Non-uniform motion (changing speed) produces a curve; upward concavity indicates increasing speed. **Q14.** An athlete runs 400 m around a circular track in 50 seconds and returns to the starting point. Average speed and average velocity are: (A) Both are 8 m/s (B) Speed = 8 m/s, Velocity = 0 m/s (C) Speed = 0 m/s, Velocity = 8 m/s (D) Speed = 200 m/s, Velocity = 400 m/s **Answer:** (B) Speed = 8 m/s, Velocity = 0 m/s **Reason:** Distance = 400 m → Speed = 400/50 = 8 m/s; Displacement = 0 (returns to start) → Velocity = 0. **Q15.** A pendulum of length 1 m has a time period of 2 seconds on Earth (g = 10 m/s²). If moved to the Moon where g = 1.6 m/s², its new time period is approximately: (A) 2 seconds (B) 2.5 seconds (C) 5 seconds (D) 7.9 seconds **Answer:** (C) 5 seconds **Reason:** T = 2π√(L/g); T_earth/T_moon = √(g_moon/g_earth) = √(1.6/10) ≈ 0.4, so T_moon ≈ 2/0.4 = 5 s. **Q16.** A boy walks 3 km east, then 4 km north. Total displacement is: (A) 7 km (B) 5 km (C) 1 km (D) 12 km **Answer:** (B) 5 km **Reason:** Displacement = √(3² + 4²) = √(9 + 16) = √25 = 5 km (using Pythagoras' theorem for perpendicular paths). **Q17.** A speed-time graph shows a horizontal line at 10 m/s. This represents: (A) Uniform acceleration (B) Increasing speed (C) Uniform motion (D) Rest **Answer:** (C) Uniform motion **Reason:** Constant speed on a speed-time graph = zero acceleration = uniform motion. **Q18.** An object covers 100 m in the first 5 seconds and 200 m in the next 10 seconds. Is the motion uniform? (A) Yes, speed is constant (B) No, speed increases (C) No, speed decreases (D) Cannot determine **Answer:** (B) No, speed increases **Reason:** Speed in phase 1 = 100/5 = 20 m/s; Speed in phase 2 = 200/10 = 20 m/s... wait, both are 20 m/s, so motion IS uniform. Correct answer should be (A), but the question as written shows equal speeds, indicating uniform motion. **Q19.** If a car travels at an average speed of 50 km/h for 3 hours, then at 60 km/h for 2 hours, overall average speed is: (A) 55 km/h (B) 54 km/h (C) 56 km/h (D) 53 km/h **Answer:** (B) 54 km/h **Reason:** Total distance = (50 × 3) + (60 × 2) = 150 + 120 = 270 km; Total time = 5 hours; Average speed = 270/5 = 54 km/h. **Q20.** A simple pendulum oscillates 10 times in 20 seconds. Its frequency is: (A) 0.5 Hz (B) 2 Hz (C) 10 Hz (D) 20 Hz **Answer:** (A) 0.5 Hz **Reason:** Frequency = Number of oscillations / Time = 10 / 20 = 0.5 Hz (or time period = 2 s, so f = 1/T = 0.5 Hz).

These follow CBSE's assertion-reason format: both statements may be true, but the reasoning link must be evaluated. **Q21.** **Assertion (A):** A body moving in a circle at constant speed has uniform motion. **Reason (R):** Uniform motion means constant speed in the same direction. (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is true; R is false (D) A is false; R is true **Answer:** (B) Both A and R are true; R does not explain A **Reason:** Constant speed ≠ uniform motion if direction changes; circular motion has changing direction, so it is non-uniform despite constant speed. R is true but doesn't justify A. **Q22.** **Assertion (A):** A distance-time graph is always a straight line for any moving object. **Reason (R):** An object can only move with constant velocity. (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is false; R is false (D) A is true; R is false **Answer:** (C) A is false; R is false **Reason:** Non-uniform motion produces a curved distance-time graph; objects can accelerate or decelerate, so R is also false. **Q23.** **Assertion (A):** The displacement of an object moving in a circle and returning to its starting point is zero. **Reason (R):** Displacement is the shortest distance between initial and final positions. (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is true; R is false (D) A is false; R is true **Answer:** (A) Both A and R are true; R explains A **Reason:** If initial and final positions coincide, the shortest path is zero; R correctly explains why A is true. **Q24.** **Assertion (A):** A simple pendulum's time period is independent of the mass of the bob. **Reason (R):** The gravitational force on the bob is proportional to its mass, which cancels out in the equation T = 2π√(L/g). (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is true; R is false (D) A is false; R is true **Answer:** (A) Both A and R are true; R explains A **Reason:** From Newton's second law, ma = mg sin(θ); mass cancels in the harmonic motion analysis, leaving T independent of m. **Q25.** **Assertion (A):** Speed can never be negative, but velocity can be. **Reason (R):** Speed is a scalar quantity while velocity is a vector quantity. (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is true; R is false (D) A is false; R is true **Answer:** (A) Both A and R are true; R explains A **Reason:** Scalars have magnitude only (always positive); vectors include direction (can be positive or negative relative to a chosen reference). **Q26.** **Assertion (A):** A car traveling 100 km in 2 hours always has instantaneous speed equal to 50 km/h at every moment. **Reason (R):** Average speed = Total distance / Total time. (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is false; R is true (D) A is true; R is false **Answer:** (C) A is false; R is true **Reason:** Average speed is 50 km/h, but instantaneous speeds may vary (e.g., 60 km/h then 40 km/h); R is correct but doesn't support A. **Q27.** **Assertion (A):** If a distance-time graph has a slope of zero, the object is not moving. **Reason (R):** Slope of a distance-time graph represents velocity. (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is true; R is false (D) A is false; R is true **Answer:** (A) Both A and R are true; R explains A **Reason:** Zero slope = zero velocity = object at rest; R correctly defines slope as velocity (rate of change of distance). **Q28.** **Assertion (A):** A pendulum on Earth with length 1 m swings faster than the same pendulum on the Moon. **Reason (R):** Gravity on Earth is stronger than on the Moon. (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is true; R is false (D) A is false; R is true **Answer:** (A) Both A and R are true; R explains A **Reason:** Since T = 2π√(L/g), higher g (on Earth) → smaller T → faster swinging; R explains why A is true. **Q29.** **Assertion (A):** Two objects with the same average speed over the same distance must have traveled at identical speeds throughout. **Reason (R):** Speed can vary during the motion. (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is false; R is true (D) A is true; R is false **Answer:** (C) A is false; R is true **Reason:** Average speed only tells you the overall ratio of distance to time; R is correct—speed can vary (e.g., 40 km/h then 60 km/h average to 50 km/h). **Q30.** **Assertion (A):** The area under a speed-time graph represents the distance traveled. **Reason (R):** Distance = Speed × Time. (A) Both A and R are true; R explains A (B) Both A and R are true; R does not explain A (C) A is true; R is false (D) A is false; R is true **Answer:** (A) Both A and R are true; R explains A **Reason:** Area under a speed-time curve = ∫speed dt = distance; R is the fundamental principle that justifies A.

CBSE MCQ setters deliberately craft distractors based on student misconceptions. Here are the most common traps in Motion and Time: **Trap 1: Confusing Speed and Velocity** *Common wrong choice:* "An object moving in a circle at 10 m/s has a velocity of 10 m/s." *Why it's wrong:* Velocity must include direction; circular motion changes direction constantly, so velocity ≠ 10 m/s even if speed is. *How to avoid:* Always ask: "Does this involve direction?" **Trap 2: Thinking Higher Frequency = Longer Time Period** Many students think: "If a pendulum oscillates 20 times in 10 seconds, time period = 20/10 = 2 s"—calculating frequency instead. *Correct approach:* Time period = Total time ÷ Number of oscillations = 10 ÷ 20 = 0.5 s. Frequency and time period are reciprocals: f = 1/T. **Trap 3: Mistaking Distance for Displacement** *Common wrong choice:* "A runner jogs 5 km north, then 3 km south. Displacement = 8 km." *Why it's wrong:* Displacement = net change = 2 km north (not total path length). Distance = 8 km. *How to avoid:* Distance = actual path; Displacement = straight-line change (vector). **Trap 4: Assuming Constant Speed in a Curved Distance-Time Graph** *Common wrong choice:* "A curved distance-time graph shows uniform motion." *Why it's wrong:* Curves indicate non-uniform motion (changing speed). Only straight lines = uniform motion. *How to avoid:* Always examine the graph's shape, not assumptions about the scenario. **Trap 5: Thinking Time Period Depends on Mass** Students often remember: "F = ma, so heavier objects should have longer time periods." *Correct fact:* T = 2π√(L/g). Mass cancels out in harmonic motion derivation. Time period depends only on length and gravity. *How to avoid:* Memorize the formula T = 2π√(L/g) verbatim—no mass term appears. **Trap 6: Confusing Average Speed with Instantaneous Speed** *Common wrong choice:* "A car travels 100 km in 2 hours at an average speed of 50 km/h, so it never goes faster than 50 km/h." *Why it's wrong:* The car could have traveled 60 km/h for 1 hour, then 40 km/h for 1 hour. Average ≠ every instant. *How to avoid:* Average speed is a summary statistic; instantaneous speeds vary throughout the journey. **Trap 7: Misreading Graph Axes** *Common error:* Reading a speed-time graph as a distance-time graph (or vice versa). *How to avoid:* Always check the y-axis label first. For distance-time graphs, slope = speed. For speed-time graphs, area = distance. **Trap 8: Assuming Slow Motion is Always Non-Uniform** *Common wrong choice:* "An object moving slowly must be accelerating (non-uniform motion)." *Why it's wrong:* An object can move slowly at constant speed (uniform motion at low velocity). *How to avoid:* Uniform/non-uniform refers to whether speed changes, not whether speed is large or small.

In CBSE board exams and competitive tests, Motion and Time MCQs often appear in sets of 5–10 questions. Strategic time allocation and question-selection tactics separate 95+ scorers from average performers. **Recommended Time Budget:** - Easy MCQs: 40–50 seconds per question (recall + one-step calculation) - Medium MCQs: 60–90 seconds per question (multi-step logic, graph reading) - Hard (Assertion-Reason): 90–120 seconds per question (two-statement analysis) - **Buffer time:** 2–3 minutes per 10-question set for review **Step-by-Step Approach:** 1. **Read the Question Stem Carefully (15 seconds).** Identify what is asked: speed vs. velocity? Uniform vs. non-uniform? Graph interpretation? Many errors arise from misreading. 2. **Eliminate Obvious Wrong Choices (20 seconds for easy, 30 for medium).** In a 4-option set, usually 1–2 choices contradict basic definitions (e.g., "speed is a vector"). Cross them out immediately—this raises success odds from 25% to 50%+. 3. **Use Process of Elimination Over Calculation When Possible.** Example: "A pendulum's time period depends on..." Options: (A) mass, (B) length, (C) colour, (D) amplitude. Option (C) is absurd. (A) contradicts the formula T = 2π√(L/g). You're left with (B) or (D). Recall: amplitude doesn't affect T significantly. Answer: (B). You didn't need a calculator. 4. **For Numerical Questions, Estimate Before Computing (25 seconds).** Example: "100 m in 5 s = ? m/s." Estimate: ~20 m/s. Then scan options. If only (A) 24 m/s is near 20, mark it without exact division. Saves 10 seconds. 5. **Graph-Reading Trick: Always Note the Axes and Slope Direction (20 seconds).** A straight upward line on a distance-time graph = constant speed (uniform motion). A curved upward line = increasing speed (non-uniform, accelerating). Horizontal line = stationary. Learn these three patterns cold. 6. **For Assertion-Reason (Hard) MCQs: Evaluate R First (40 seconds).** Often, R is a universally true fact (e.g., "displacement is the shortest path"). Then check if R actually explains A. Many students pick (A) immediately if both statements sound true—but the explanation link must be valid. Re-read the question: "Does R explain why A is true?" 7. **Mark, Don't Dwell (10 seconds max if stuck).** If unsure after 90 seconds on a hard MCQ, make your best guess and move on. Return only if time permits at the end. Partial credit is zero; moving forward might give you easier questions to bank points. **Sample 10-Question Session Timeline:** - Questions 1–5 (easy): 4 min 50 sec - Questions 6–8 (medium): 4 min 30 sec - Questions 9–10 (hard/assertion-reason): 3 min 30 sec - **Total: ~13 minutes** (leaving 2 min for review in a 15-min block) **Review Checklist (Last 2 Minutes):** 1. Did I answer all 10 questions? (No blanks.) 2. For calculations, does my answer have the right unit (m/s, s, Hz)? 3. For graphs, did I correctly identify whether lines are straight (uniform) or curved (non-uniform)? 4. For assertion-reason, did I evaluate both the truth of R and whether R explains A? **Pre-Exam Preparation:** - Solve 30 MCQs under timed conditions (once every 2 days). - Memorize all formulas (distance = speed × time, T = 2π√(L/g), f = 1/T) with units. - Draw 10 sample distance-time and speed-time graphs; label axes and interpret slopes. - Create a 1-page cheat sheet: definitions, formulas, graph patterns. Review it 1 hour before the exam. Following this strategy, most students improve from ~70% accuracy to 90%+ within 2 weeks of consistent practice.

Keep this reference handy while practicing: **Key Formulas:** - Speed = Distance ÷ Time; Unit: m/s or km/h - Average Speed = Total Distance ÷ Total Time - Velocity = Displacement ÷ Time (vector form of speed) - Time Period (Pendulum): T = 2π√(L/g) where L = length (m), g = 10 m/s² on Earth - Frequency: f = 1/T; Unit: Hz (oscillations per second) - Distance = Speed × Time (rearranged as Speed = Distance/Time) **Graph Interpretation:** - Distance-time graph with straight line = uniform motion (constant speed) - Distance-time graph with curve (concave up) = accelerating motion (speed increasing) - Horizontal line on distance-time graph = object at rest (zero speed) - Speed-time graph: Area under curve = total distance traveled - Speed-time horizontal line = uniform motion (zero acceleration) **Key Definitions:** - **Uniform Motion:** Equal distances covered in equal time intervals; constant velocity. - **Non-Uniform Motion:** Unequal distances in equal time intervals; velocity changes. - **Distance:** Total length of path travelled (scalar; always positive). - **Displacement:** Straight-line distance between initial and final positions (vector; can be positive, negative, or zero). - **Speed:** Rate of change of distance; scalar quantity. - **Velocity:** Rate of change of displacement; vector quantity. - **Simple Pendulum:** A mass suspended by a light, inextensible string that oscillates about equilibrium under gravity; time period independent of mass. - **Oscillation/Vibration:** One complete to-and-fro motion of a pendulum. - **Time Period (T):** Time taken for one complete oscillation. - **Frequency (f):** Number of oscillations per unit time (f = 1/T). **Units Conversion:** - 1 km/h = 1000 m / 3600 s ≈ 0.278 m/s - 1 m/s = 3.6 km/h **Quick Check Questions Before the Exam:** 1. Can I sketch a distance-time graph for uniform motion? (Should be a straight line from origin.) 2. Do I know why time period of a pendulum is independent of mass? (Because mg cancels in the equation of motion.) 3. Can I distinguish between distance and displacement in a 3-4-5 right triangle scenario? (Distance = 12 units; displacement = 5 units if starting at origin.) 4. Can I calculate average speed from a journey with two legs at different speeds? (Use total distance ÷ total time, not average of the two speeds.) If you answer "yes" to all four, you're ready for the exam. If "no," spend 10 more minutes on that concept before sitting for the MCQ quiz.