Important Questions Class 11 Physics Chapter 3

Important Questions for CBSE Class 11 Physics Chapter 3

Important Questions for CBSE Class 11 Physics Chapter 3 – Motion in a Straight Line

In Chapter 3, Motion in a Straight Line of Class 11 Physics, students will learn about relative velocity and its derivations. The chapter also discusses acceleration and how it relates to speed and velocity. After that, students will look at kinematic equations and uniformly accelerated motion. 

Extramarks Important Questions for Class 11 Physics Chapter 3 makes it easier to study for students who prefer learning in a question-answer format. These questions are compiled by subject matter experts and are written in clear, simple language. 

CBSE Class 11 Physics Chapter 3 Important Questions

Study Important Questions for Class 11 Physics Chapter 3 – Motion in A Straight Line 

Some of the 1-mark, 2-marks, 3-marks, 4-marks, and 5-marks Class 11 Physics Chapter 3 Important Questions are discussed below. Students can access the link on the Extramarks website to review additional questions. 

1 Mark Answers and Questions

Q1. Two balls of varying masses are launched vertically upward at the same initial speed. Which will reach the highest point?

A1. If two balls of different masses are thrown vertically upward at the same initial speed, they will both rise to a greater height.

Q2. Can an object’s speed be negative? Justify.

A2. An object’s speed can never be negative. This is due to the fact that the distance is always positive.

2 Marks Answers and Questions

Q1. Give the characteristics of displacement.

A1. The characteristics of displacement are as follows.

(1) Displacement is a vector quantity that has magnitude as well as direction.

(2) A given body’s displacement can be positive, negative, or zero.

Q2. What causes a particle’s velocity to vary?

A2. The velocity of a particle varies when

(1) changes in velocity magnitude.

(2) the motion’s direction shifts.

3 Marks Answers and Questions

Q1. A stone is dropped from the top of a cliff and found to travel 44.1m before diving at the last second. What is the cliff’s height? (g = 9.8m/s2)

A1. Consider the height of the cliff to be h.

u = 0m/s,

a = g = 9.8m/s2.

If n is the total time taken by the stone while falling,

Snth = u+a2(2n−1) 

44.1 = 0+9.82(2n−1) 

N = 102 = 5s

Now,

h = ut+12at2 

h = 12(9.8)(5)2 = 122.5m, which is the required height.

Q2. A woman leaves her house at 9.00 a.m., walks at a speed of 5 km/hr on a straight road to her office, which is 2.5 km away, works there until 5.00 p.m., and then returns home by auto at a speed of 25 km/hr. Select appropriate scales and draw the x-t graph of her motion.

A2.  It is given that:

Speed of the woman  = 5 km/h 

Distance between her office and home  = 2.5 km 

Time taken = Distance / Speed 

= 2.5 / 5 = 0.5 h = 30 min 

It is given that she covers the same distance in the evening by auto.

Now, the speed of the auto = 25 km/h 

Time taken = Distance / Speed 

= 2.5 / 25 = 1 / 10 = 0.1 h = 6 min 

4 Marks Answers and Questions

Q1. Regular bus service connects two towns, A and B, with a bus leaving in either direction every T minutes. A man cycling at 20 km/hr from A to B notices that a bus passes him every 18 minutes in the direction of his motion and every 6 minutes in the opposite direction. What is the bus service period T, and at what speed (assumed constant) do the buses travel on the road?

A1. 

Consider V to be the speed of the bus running between towns A and B.

In the question, it is given that:

Speed of the cyclist is  v=20 km/hr 

The relative speed of the bus moving in the direction of the cyclist will be V−v = (V−20)m/s.

The bus went past the cyclist every 18 min, i.e.,  18 / 60 h  (when he moves in the direction of the bus).

Hence, distance covered by the bus  = (V − 20) × 18 / 60 km …. (i)

As one bus leaves after every T minutes, 

the distance travelled by the bus will be  = V × T / 60 …. (ii)

As equations (i) and (ii) are equal,

(V − 20) × 18 / 60 = V × T / 60 ….. (iii)

The relative speed of the bus moving in the opposite direction of the cyclist will be (V + 20) km/h. 

Thus, the time taken by the bus to go past the cyclist  = 6 min = 6 / 60 hr. 

⇒(V + 20)×6 / 60 = V × T / 60 …. (iv)

From (iii) and (iv), we get

(V + 20) × 6 / 60 = (V − 20) × 18 / 60 

V + 20 = 3V  60 

2V = 80 

V = 40 km/h, which is the required speed.

Substituting the value of V in equation (iv), 

(40 + 20) × 6 / 60 = 40 T / 60 

T = 360 / 40 = 9 min, which is the required time period.

5 Marks Answers and Questions

Q1. A man walks from his house to a market 2.5 kilometres away at a speed of 5 kilometres per hour on a straight road. When he discovers that the market is closed, he immediately turns around and walks back home at a speed of 7.5 km/h. What exactly is the

(a) the average velocity magnitude, and

(b) the average speed of the man over the time intervals? 

(i) 0 to 30 minutes 

(ii) 0 to 50 minutes 

(iii) 0 to 40 minutes 

(Note: This exercise will show you why it is better to define average speed as total path length divided by time rather than average velocity magnitude. You don’t want to tell the tired man on his way home that his average speed was 0.)

A1. In the question, it is given that,

Time taken by the man to reach the market from home is t1 = 2.5/5 = 1/2hr = 30min.

Time taken by the man to reach home from the market is t2 = 2.5/7.5 = 1/3hr = 20min. 

Total time taken in the whole journey  = 30 + 20 = 50 min 

1. i) 0 to 30 min

Average velocity = Displacement/Time 

Average speed = Distance/Time 

1. ii) 0 to 50 min

Time = 50 min = 50/60 = 5/6 h 

Net displacement = 0 

Total distance = 2.5 + 2.5 = 5 km 

Average velocity = Displacement / Time = 0 

Average speed = Distance / Time = 5/(5/6) = 6 km/h 

iii) 0 to 40 min

Speed of the man = 7.5 km/h 

Distance travelled in first 30 min = 2.5 km 

Distance travelled by the man (from the market to home) in the next 10 min

= 7.5 × 10/60 = 1.25 km 

Net displacement = 2.5  1.25 = 1.25 km 

Total distance travelled = 2.5 + 1.25 = 3.75 km 

Average velocity = Displacement / Time = 1.25 / (40/60) = 1.875 km/h 

Average speed = Distance / Time = 3.75 / (40/60) = 5.625 km/h

Important Questions for Chapter 13 Physics Class 11

The chapter is full of theories and concepts that require clear understanding to grasp them and score the best possible marks. Studying and practising are two of the best ways to learn this chapter. Students should take the time to answer the important questions, as this will help them get good grades. They must also learn the theories and practise the chapter’s practical aspects. Through Class 11 Physics Chapter 3 Important Questions, students can test their understanding of the chapter. This will encourage them to write efficient answers in their exams.

Class 11 Physics Chapter 3 Important Questions

Some of the topics that will be covered in this chapter are as follows.

Motion is one of the most important topics in the chapter on motion in a straight line. 

Everything in the solar system is in motion. An object is said to be in motion if its position changes from one location to another over time. Motion is a relative concept, and when a body changes positions, it is always in relative motion.

Types of Motion: The type of motion is an important topic that is  part of the motion in a straight line. It is critical to understand an object’s precise location. We need to know the object’s coordinate positions. The number of coordinate positions varies depending on the type of object. There are occasionally two or three coordinates.

Displacement: It is an important topic related to motion in a straight line. Displacement is the position of an object at a given time or the change in the direction of the object during that time. It is a vector that is drawn from the beginning to the end.

Uniform Speed and Uniform Velocity: An object is said to move at a uniform speed if it travels the same distance in the same amount of time. The time intervals can be small or large, but they must be equal.

When an object moves with uniform velocity, it covers the same amount of distance in equal intervals of time. The time intervals can be small or large, but they must be equal.

Variable Speed and Variable Velocity: An object moves with variable speed when it travels unequal distances in equal amounts of time. The time span can be short or long.

When an object moves with variable velocity, it covers an unequal amount of distance in equal intervals of time. Time intervals can be short or long.

Important Questions for Motion in a Straight Line Class 11

Some of the questions that are most likely to appear in the board examinations from Class 12 Physics Chapter 3 are as follows.

• When is the condition of the relationship s = ut correct?

• If two balls of different masses are thrown vertically upward with alike initial speeds, which one will rise to a higher height?  

• Under what circumstances is the relative velocity of two bodies equal?

To access the complete set of Extramarks Important Questions Class 11 Physics Chapter 3, visit the link provided below.

Benefits of Important Questions For Class 11 Science Chapter 3

These important questions will assist students in achieving high marks and excelling in their board exams. Some of the key benefits of Class 11 Physics Chapter 3 Important Questions include the following.

• Before compiling a list of Important Questions, the subject matter experts at Extramarks conduct thorough research to ensure that the questions on the list have the highest likelihood of appearing in the exams.

• The Important Questions for Class 11 Physics Chapter 3 are in accordance with the CBSE board format, and the answers to these Important Questions are given in such a detailed and explanatory manner that all students can understand them comprehensively.

Conclusion

Students who want  help with extra study material should refer to Extramarks Class 11 Physics Chapter 3 Important Questions. It will be beneficial to the students, and they will be able to achieve the highest possible marks in the board exams. Referring to Important Questions for Class 11 Physics Chapter 3 will boost students’ confidence in passing the exam.