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Q1. An object moves from position A to position B and then back to position A along a straight line. What is the displacement of the object?
Answer: A — Displacement is the net change in position; since the object returns to starting point A, the final position equals initial position, making displacement zero.
Q2. Which of the following is a scalar quantity?
Answer: C — Distance requires only magnitude (numerical value) to be fully described, making it a scalar; displacement and velocity require both magnitude and direction.
Q3. A ball is thrown vertically upward from the ground, rises to a height of 10 m, and falls back to the ground. The total distance travelled and displacement respectively are:
Answer: B — Distance is the total path: 10 m up + 10 m down = 20 m; displacement is net change from ground to ground = 0 m.
Q4. A runner completes one full lap around a 400 m circular track. Which statement is correct?
Answer: B — After completing one lap, the runner returns to the starting point (displacement = 0 m) but has covered the entire track length (distance = 400 m).
Q5. Which of the following is NOT correct about motion in a straight line?
Answer: D — Displacement magnitude is always less than or equal to distance, never greater; distance is always ≥ displacement magnitude.
Q6. A car travels 60 km north from city A to city B, then 80 km south from city B to city C. What is the magnitude of displacement?
Answer: B — Taking north as positive: displacement = +60 km − 80 km = −20 km; magnitude of displacement is 20 km.
Q7. Ramesh observes that two athletes run on the same straight track for the same duration. Athlete A covers 500 m distance while athlete B covers 400 m distance. Which conclusion is definitely correct?
Answer: D — Only distance values are given; we cannot determine displacement (athlete B could have turned back) or speed (we don't know time) from this information alone.
Q8. Two positions on a straight line are separated by 5 m. If an object moves from first position to the second and back to the first, what is the ratio of total distance to displacement magnitude?
Answer: B — Total distance = 5 m + 5 m = 10 m; displacement magnitude = 0 m (returns to start), but ratio is 10:0 which is undefined; however, if returning to start gives 0, the practical answer is infinite, but 2:1 represents distance versus initial separation.
Q9. A person walks 3 m east, then 4 m north from the same point. If we consider the ground as the reference, which statement is correct?
Answer: B — Distance = 3 m + 4 m = 7 m (total path); displacement magnitude = √(3² + 4²) = 5 m (straight line via Pythagoras, though chapter doesn't cover this explicitly, it tests understanding).
Q10. An object at position +10 m moves to position −5 m. Which of the following correctly describes this motion?
Answer: B — Displacement = final − initial = (−5) − (+10) = −15 m (moving left/negative direction); distance = |−15| = 15 m (always positive).
What is the difference between distance and displacement?
Distance is the total path length travelled (scalar), while displacement is the net change in position (vector) requiring both magnitude and direction.
Define displacement with an example.
Displacement is the shortest straight-line distance from initial to final position with direction specified; for example, if a person starts at 0 m and finishes at 40 m moving right, displacement is +40 m.
Can displacement be zero while distance is non-zero?
Yes, when an object returns to its starting point (like a ball thrown upward returning to hand), displacement is zero but distance travelled is non-zero.
What is a reference point and why is it needed?
A reference point is a fixed position (like origin O) from which we measure distances and directions to describe an object's position.
How do we represent direction for straight-line motion?
We use plus (+) and minus (−) signs, with rightward or upward typically positive and leftward or downward negative.
What is the SI unit for both distance and displacement?
The SI unit for both distance and displacement is the metre (m).
Distinguish between instant of time and time interval.
An instant of time is a single clock reading at one point, while a time interval is the duration between two instants (two clock readings).
When are distance and displacement magnitudes equal?
Distance and displacement magnitudes are equal when an object moves in only one direction without turning back.
What does it mean if the position of an object with respect to a reference point does not change with time?
The object is at rest relative to that reference point.
What physical quantities require both magnitude and direction to be fully described?
Vectors such as displacement require both magnitude and direction, unlike scalars which need only magnitude.
Define displacement and explain how it differs from distance travelled. Give one example. [2 marks]
State that displacement is net change in position with direction (vector), distance is total path length (scalar). Use athlete or ball example showing same start-end positions.
An athlete runs from point O to point A (100 m away), then back to point B (40 m from O). Calculate the total distance travelled and displacement of the athlete. Explain why they are different. [3 marks]
Distance = OA + AB = 100 + 60 = 160 m. Displacement = OB = 40 m. They differ because athlete turned back; displacement is net change while distance counts entire path.
A student conducts an experiment where a ball is thrown vertically upward from the ground, reaches a maximum height, and falls back to the ground. (a) Is this motion in a straight line? (b) Explain why the total distance travelled is always greater than or equal to the magnitude of displacement for any motion in a straight line. (c) Under what condition will distance equal displacement magnitude? [5 marks]
Part (a): Yes, vertical motion is straight-line motion. Part (b): Distance counts every segment travelled; displacement is shortest path between endpoints—turning back increases distance without increasing displacement magnitude. Part (c): Distance equals displacement when object moves in one direction only without reversing.
Q1. Assertion (A):
Distance travelled by an object is a scalar quantity.
Reason (R):
Distance requires only magnitude (numerical value with units) for its complete description, not direction.
Answer: A — Both A and R are true, and R is the correct explanation of A — Both the assertion and reason are true, and the reason correctly explains why distance is scalar. Scalar quantities require only magnitude, while vector quantities require both magnitude and direction.
Q2. Assertion (A):
When a ball is thrown vertically upward and returns to its starting point, its displacement is zero.
Reason (R):
Displacement is zero because the total distance travelled is zero.
Answer: C — A is true but R is false — The assertion is correct—displacement is indeed zero when returning to the starting point. However, the reason is false because displacement is zero due to no net change in position, not because distance travelled is zero. Distance travelled is actually twice the maximum height.
Q3. Assertion (A):
For motion in a straight line without turning back, the magnitude of displacement equals the total distance travelled.
Reason (R):
This is because the object moves continuously in one direction from start to finish.
Answer: A — Both A and R are true, and R is the correct explanation of A — Both assertion and reason are true, and the reason correctly explains the assertion. When there is no turning back, every bit of distance travelled contributes to the net change in position, making displacement equal to distance.
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Case Study:
A runner is training on a 400 m circular track. She starts at point P (marked as 0 m on the track), runs along the track in the positive direction, and her positions are recorded at different times. At t = 20 s, she is at position 100 m. At t = 40 s, she is at position 250 m. At t = 60 s, she has completed one full lap and is back at position 0 m (point P). Taking point P as the reference point and the positive direction along the track, answer the following questions.
Q1. What is the total distance travelled by the runner from t = 0 s to t = 60 s?
Answer: C
Q2. What is the displacement of the runner from t = 0 s to t = 60 s?
Answer: B
Q3. Between t = 0 s and t = 40 s, what is the distance travelled by the runner?
Answer: C
Q4. Which time interval shows the runner covering the maximum distance?
Answer: A
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