# MCQ of Motion in a Straight Line | Chapter 3 | Physics | Class Xl | CBSE |

**MCQ of Motion in a straight line, Chapter 3, Class 11, Physics**

**Question 1: Which of the following statements is incorrect?**

- Path length is a scalar quantity where is displacement is a vector quantity
- The magnitude of displacement is always equal to the path length traversed to buy an object over a given time interval
- The displacement depends only on the end points whereas a path length depends on the actual path followed
- The path length is always positive whereas displacement can be positive negative and zero

**Answer: B (The magnitude of displacement is always equal to the path length traversed to buy an object over a given time interval)**

**Question 2: The numerical ratio of distance to displacement is**

- Always equal to one
- Always less than one
- Always greater than one
- Equal to or more than one

**Answer: D (Equal to or more than one )**

**Question 3: Which of the following statements is incorrect?**

- Displacement is independent of the choice of origin of the axis
- Displacement may or may not be equal to the distance travelled.
- When a particle returns to its starting point its displacement is not zero
- Displacement does not tell the nature of the actual motion of a particle between the points.

**Answer: C (When a particle returns to its starting point its displacement is not zero)**

**Question 4: Which of the following statements are incorrect?**

**Average velocity is path length divided by time interval**

**In general, speed is greater than the magnitude of the velocity**

**A particle moving in a given direction with a non zero velocity can have zero speed**

**The magnitude of average velocity is the average speed**

- (ii) and (iii)
- (ii) and (iv)
- (i), (iii) and (iv)
- All four

**Answer: C ( (i), (iii) and (iv) )**

**Question 5: A car is moving along a straight line OP as shown in the figure. It moves from O to P in 18 seconds and returns from P to Q in 6 seconds. Which of the following statements is not correct regarding the motion of the car?**

- The average speed of the car in going from O to P and come back to Q is 20 ms
^{-1} - The average velocity of the car in going from O to P and come back to Q is 10 ms
^{-1} - The average speed of the car in going from O to P and come back to O is 20ms
^{-1} - The average velocity of the car in going from O to P and come back to O is 20ms
^{-1}

**Answer: D ( The average velocity of the car in going from O to P and come back to O is 20ms ^{-1} )**

**Question 6: The area under velocity time graph for a particle in a given interval of time represents**

- Velocity
- Acceleration
- Work done
- Displacement

**Answer: D (Displacement)**

**Question 7: The position of an object moving along x-axis is given by x = a + bt ^{2}, where a = 8.5 m and b = 2.5 ms^{-2} and t is measured in seconds. The average velocity of the object between t = 2 s and t = 4 s is**

- 5 ms
^{-1} - 10 ms
^{-1} - 15 ms
^{-1} - 20 ms
^{-1}

**Answer: C (15 ms ^{-1})**

**Question 8: A boy walks on a straight road from his home to a market 2.5 kilometre with a speed of 5 km h ^{-1}. Finding the market closed he instantly dance and walks back with a speed of 7.5 km h^{-1}. What is the average speed and average velocity of the boy between t=0 to t=50 min?**

- 0,0
- 6km h
^{-1}, 0 - 0, 6 km h
^{-1} - 6 km h
^{-1}, 6 km h^{-1}

**Answer: B (6 km h ^{-1}, 0)**

**Question 9: Speedometer of a car measures**

- Average speed
- Average velocity
- Instantaneous speed
- Instantaneous velocity

**Answer: C (Instantaneous speed)**

**Question 10: A particle moves with uniform velocity. Which of the following statements about the motion of particle is true?**

- Its speed is zero
- Its acceleration is zero
- Its acceleration is opposite to the velocity
- Its speed may be variable

**Answer: B (Its acceleration is zero)**

**You may also read MCQ of Physical World, MCQ of Units and Measurements, MCQ of Motion in a Plane, MCQ of Laws of Motion, MCQ of Work, Energy and Power, MCQ of System of Particles and Rotational Motion, MCQ of Gravitation for better understanding of the chapters.**

**Question 11: The motion of a particle is described by the equation x = at + bt ^{2} , where a = 15 cm s^{-1} and b = 3 cm s^{-2} . Its instantaneous velocity at t = 3 s will be**

- 33 cm s
^{-1} - 18 cm s
^{-1} - 16 cm s
^{-1} - 32 cm s
^{-1}

**Answer: A (33 cm s ^{-1})**

**Question 12: The displacement of a body is given to the proportional to the cube of time elapsed. The magnitude of the acceleration of the body is**

- Increasing with time
- Decreasing with time
- Constant but not zero
- Zero

**Answer: A (Increasing with time)**

**Question 13: The area under acceleration time graph represents the**

- Initial velocity
- Final velocity
- Change in velocity
- Distance travelled

**Answer: C (Change in velocity)**

**Question 14: Which of the following statements is not correct regarding the motion of a particle in a straight line?**

- x-t graph is a parabola, if motion is uniformly accelerated
- v-t is a straight line inclined to the time axis if motion is uniformly accelerated
- x-t graph is a straight line in client to the time access if motion is uniform and acceleration is zero
- v-t graph is a parabola if motion is uniform and acceleration is zero

**Answer: D (v-t graph is a parabola if motion is uniform and acceleration is zero)**

**Question 15: Which of the following statements is not correct ?**

- The zero velocity of a body at any instant does not necessarily imply zero acceleration at that instant
- The kinematics equation of motion are true only for motion in which the magnitude and the direction of acceleration are constant during the course of motion
- The sign of acceleration tell us whether the particles speed is increasing or decreasing
- All of these

**Answer: C (The sign of acceleration tell us whether the particles speed is increasing or decreasing)**

**Question 16: A player throws a ball vertically upwards with velocity u. At highest point,**

- Both the velocity and acceleration of the ball are zero
- The velocity of the ball is u but its acceleration is zero
- The velocity of the ball is zero but its acceleration is g
- The velocity of the ball is u but its acceleration is g

**Answer: C (The velocity of the ball is zero but its acceleration is g)**

**Question 17: A girl standing on a stationary lift (open from above) throws a ball of words with initial speed 50 ms ^{-1}. The time taken by the ball to return to her hands is**

- 5 s
- 10 s
- 15 s
- 20 s

**Answer : B (10 s)**

**Question 18: A man is standing on the top of building 100 m high. He throws two balls vertically upwards one at t=0 and other after a time interval (less than 2 s). The later ball is thrown at a velocity of half the first. The vertical gap between first and second ball is 15 m at t=2 s. The gap is found to remain constant. The velocities with which the balls were thrown are**

- 20 ms
^{-1}, 10 ms^{-1} - 10 ms
^{-1}, 5 ms^{-1} - 16 ms
^{-1}, 8 ms^{-1} - 30 ms
^{-1}, 15 ms^{-1}

**Answer: A ( 20 ms ^{-1}, 10 ms^{-1})**

**Question 19: A ball is thrown vertically upwards with a velocity of 20 m s ^{-1} from the top of a multi-storey building of 25 m high. How high will the ball rise?**

- 10 m
- 15 m
- 20 m
- 25 m

**Answer: C (20 m)**

**Question 20: Two trains A and B each of length 400 m are moving on two parallel tracks with uniform speed 72 km h ^{-1} in the same direction with A ahead of B. The driver of B decides to overtake A and accelerates by 1 m s^{-2}. If after 50 s, the guard of B just brushes past A, what was the original distance between them?**

- 750 m
- 1000 m
- 1250 m
- 2250 m

**Answer: C (1250 m)**

**Question 21: A boy covers a distance of 4 m in 3rd second and 12 m in 5th second. If the motion is uniformly accelerated, how far will it travel in the next 3 seconds?**

- 10 m
- 30 m
- 40 m
- 60 m

**Answer: D (60 m)**

**Question 22: A bullet fired into a wooden block loses half of its velocity after penetrating 40 cm. It comes to rest after penetrating if for the distance of**

- 22 / 3 cm
- 40 / 3 cm
- 20 / 3 cm
- 22 / 5 cm

**Answer: B (40 / 3 cm)**

**Question 23: An object flowing through a fluid is observed to have acceleration given by a = g – bv where g = gravitational acceleration and b is constant. After a long time of release it is observed to fall with constant speed. The value of constant speed is**

- g / b
- b / g
- bg
- b

**Answer : A (g / b)**

**Question 24: A ball is dropped from a building of height 45 m. Simultaneously another identical ball B is thrown up with a speed of 50 m s ^{-1}. The relative speed of ball B w.r.t. ball A at any instant of time is**

- 0
- 10 m s
^{-1} - 25 m s
^{-1} - 50 m s
^{-1}

**Answer: D (50 m s ^{-1})**

**Question 25: A ball is thrown vertically upwards with speed u. At the same instant another ball B is released from rest at height h. At time t the speed of a relative to B is**

- u
- u – 2 g t
- √u
^{2}– 2 g h - u – gt

**Answer: A ( u )**

**Question 26: Two cars A and B are running at velocities of 60 km h ^{-1} and 45 km h^{-1}. What is the relative velocity of car with respect to car B if both are moving eastward?**

- 15 km h
^{-1} - 45 km h
^{-1} - 60 km h
^{-1} - 105 km h
^{-1}

**Answer: A (15 km h ^{-1})**

**Question 27: A bus is moving with a speed of 10 m s ^{-1} on a straight road. A scooterist wishes to overtake the bus in 100 s. If the bus is at a distance of 1 km from the scooterist with what speed should the scooterist chase the bus?**

- 40 m s
^{-1} - 25 m s
^{-1} - 10 m s
^{-1} - 20 m s
^{-1}

**Answer: D (20 m s ^{-1})**

**Question 28: Two towns A and B are connected by a regular bus service with a bus living in either direction every T minutes. A man cycling with a speed of 20 km h ^{-1} in the direction A to B notices that a bus goes past him every 18 min in the direction of his motion, and every 6 min in the opposite direction. The time period T of the bus service is**

- 4.5 min
- 9 min
- 12 min
- 24 min

**Answer: B (9 min)**

**Question 29: Two parallel rail tracks run North- South. On one track train A moves north with a speed of 54 km h ^{-1} and on the other track train B moves South with a speed of 90 km h^{-1}. The velocity of train A with respect to train B**

**is**

- 10 m s
^{-1} - 15 m s
^{-1} - 25 m s
^{-1} - 40 m s
^{-1}

**Answer: D (40 m s ^{-1} )**

**Question 30: A train which is 120 m long is running with velocity 20 m/s while train B which is 130 m long is running in opposite direction with velocity 30 m/s. What is the time taken by train B to cross the train A?**

- 5 s
- 25 s
- 10 s
- 100 s

**Answer: A (5 s)**

**Question 31: On a long horizontally moving belt a child runs to and fro with a speed 9 km h ^{-1} (with respect to the belt) between his father and mother located 50 m apart on the moving belt. The belt moves with a speed of 4 km h^{-1}. For an observer on a stationary belt the speed of the child running in the direction of motion of the belt is**

- 4 km h
^{-1} - 5 km h
^{-1} - 9 km h
^{-1} - 13 km h
^{-1}

**Answer: D (13 km h ^{-1})**

**Question 32: In one dimensional system instantaneous v satisfies 0 ≤ v < v _{o}**

- The displacement in time T must always take non negative values
- The displacement x in time T satisfies -v
_{o}T < x < v_{o}T - The acceleration is always a non negative number
- The motion has no turning points

**Answer: B (The displacement x in time T satisfies -v _{o}T < x < v_{o}T)**

**Question 33: The displacement of a particle is given by x = (t – 2) ^{2} where X is in metres and T in seconds . The distance covered by the particle in first 4 seconds is**

- 4 m
- 8 m
- 12 m
- 16 m

**Answer: B (8 m)**

**Question 34: A particle is moving on a circular path of radius R with constant speed v. During motion of the particle from point A to point B**

- Average speed is v/2
- The magnitude of average velocity is v/π
- The magnitude of average acceleration is 2v
^{2}/ πR - Average velocity is zero

**Answer: C (The magnitude of average acceleration is 2v ^{2}/ πR)**

**Question 35: A police party is moving in a jeep at a constant speed v. They saw a thief at a distance x on a motorcycle which is at rest. At the same moment the thief saw the police and he started at constant acceleration a. Which of the following relations is true if the police is able to catch the thief?**

- v
^{2}< ax - v
^{2}< 2ax - v
^{2}≥ 2ax - v
^{2}= ax

**Answer : C (v ^{2} ≥ 2ax)**

**Question 36: A juggler keeps n balls going with one hand, so that at any instant (n – 1) balls are in air and one ball in the hand. If each ball rises to a height of x metres, the time for each ball to stay in his hand is**

- 1/n-1 √2x / g
- 2/n-1 √2x / g
- 2/n √2x / g
- 1/n √2x / g

**Answer: B ( 2/n-1 √2x / g)**

**Question 37: Two trains 121 and 99 m in length are running in opposite directions with velocities 40 km h ^{-1} and 32 km h^{-1}. In what time they will completely cross each other?**

- 9 s
- 11 s
- 13 s
- 15 s

**Answer: B (11 s)**

**Question 38: A ball is dropped from the top of a building 100 m high. At the same instant another ball is thrown upwards with a velocity of 40 m/s from the bottom of the building. The two balls will meet after**

- 3 s
- 2 s
- 2.5 s
- 5 s

**Answer: C (2.5 s)**

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Very informative!

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