Long Questions: Motion and Measurement of Distances | NCERT Summary: UPSC PDF Download

Q1: Classify the following as circular, periodic or rectilinear motion: Playing a mridangam, Carousel, Swing, Speed boat racing ahead, 100m dash, Shuttlecock during a game of badminton, weather vane, rocking chair, a penalty kick in a game of football, aeroplane during take-off.
Ans: The classification of the motions is as given below:

Q2: Compare rectilinear motion with circular motion.
Ans: Comparisons between rectilinear and circular motion are as given below:

Q3: What are the different types of motion? Explain with examples.
Ans: Motions can be divided into three categories:
Rectilinear Motion: 

• An object moves in a straight path in this sort of motion.
• The object's direction may change from time to time, but it always moves in a straight line.
• Examples include a car travelling down a straight road, an aeroplane flying, and a ball rolling on the ground.

Circular Motion:

• The object moves in a circular motion in this form of motion.
• The object moves, but the distance between it and the origin remains constant. 
• For example, clock hands, fan blades, windmill blades, and so on.

Periodic Motion:

• In this form of motion, an item moves in a sequential manner.
• A similar motion is repeated by the object on a regular basis. 
• For example, swing movement, drumming, and so on.

Q4: Explain the concept of motion and its types. Provide examples to illustrate each type of motion and describe how they are different from each other.
Ans: Motion refers to the change in position of an object over time.
There are three types of motion:

• Translatory Motion: In this type of motion, an object moves in a straight line. For example, a car moving along a highway or a train on its tracks.
• Rotatory Motion: An object rotates about a fixed point or an axis. A spinning top, a fan blade, or a merry-go-round are examples of rotatory motion.
• Vibratory Motion: An object moves back and forth around a central point. A swinging pendulum, a vibrating guitar string, or a tuning fork exhibit vibratory motion.

These types of motion help us understand how objects move in different ways and are observed in our daily lives.

Q5: Describe the difference between distance and displacement. Provide examples to illustrate each concept and explain why displacement can be smaller than distance traveled.
Ans: Distance is the total length of the path covered by an object. It is a scalar quantity and is always positive. For example, if you walk 3 kilometers north and then 4 kilometers south, your total distance traveled is 7 kilometers.
Displacement, on the other hand, is the shortest distance between the initial and final positions of an object in a straight line. It is a vector quantity and can be positive, negative, or zero. In the above example, your displacement would be 1 kilometer south, as you've ended up 1 kilometer away from your starting point.
Displacement can be smaller than distance when the object returns to its starting point. It considers only the change in position, while distance accounts for the entire path traveled.

Q6: Explain the concept of speed and how it is calculated. Differentiate between average speed and instantaneous speed. Provide examples to illustrate each type of speed.
Ans: Speed is the rate of change of distance with respect to time. It tells us how fast an object is moving. Speed is calculated using the formula:
Speed = Distance / Time
Average Speed is the total distance traveled divided by the total time taken. For example, if a car travels 300 kilometers in 6 hours, its average speed is 300 km / 6 hrs = 50 km/h.
Instantaneous Speed is the speed at a specific instant in time. It may vary during the motion. For instance, the speedometer of a car shows its instantaneous speed at any given moment.
Example: If a person covers a distance of 100 meters in 20 seconds, their average speed is 100 m / 20 s = 5 m/s. However, their instantaneous speed might be higher or lower at different points during the 20 seconds.

Q7: Describe the concept of a distance-time graph and how it helps in understanding motion. Provide examples of different types of distance-time graphs and explain their corresponding motions.
Ans: A distance-time graph is a graphical representation of an object's motion, with time on the x-axis and distance on the y-axis. It helps us visualize the motion and understand its characteristics.
Interpreting Distance-Time Graphs:

• Straight Line: A straight line indicates uniform motion, where the object covers the same distance in equal time intervals. The slope of the line represents speed.
• Horizontal Line: A horizontal line means the object is at rest; it's not covering any distance.
• Curved Line: A curved line indicates non-uniform motion, where the object covers different distances in equal time intervals. The steeper the curve, the faster the motion.
• Example: If a car moves at a constant speed of 60 km/h, its distance-time graph would be a straight line with a positive slope. If a person walks and then runs, the graph might show a curved line, indicating varying speeds.

Q8: Explain the need for measuring time accurately and the concept of a stopwatch. Provide examples of situations where accurate time measurement is crucial.
Ans: Accurate time measurement is essential for various activities to ensure coordination, efficiency, and safety.

• Stopwatch: A stopwatch is a device used to measure time intervals accurately. It typically has a start button, stop button, and reset button. When the start button is pressed, the timer begins counting, and when the stop button is pressed, the timer stops, showing the elapsed time.

Importance of Accurate Time Measurement:

• Sports: In sports events, accurate timing determines winners, records, and rankings.
• Cooking: Precise timing is necessary for recipes that require specific cooking durations.
• Science Experiments: Accurate timing is crucial for reliable data collection and analysis in experiments.
• Transportation: Timetables and schedules in transportation systems ensure punctuality and efficient services.

A stopwatch helps in measuring time intervals with precision, allowing tasks to be performed accurately and efficiently in various contexts.

Q9: Explain the concept of uniform and non-uniform motion. Provide examples to illustrate each type of motion and describe how they differ from each other.
Ans: Uniform Motion is when an object covers equal distances in equal intervals of time. For example, a car moving at a constant speed of 40 km/h covers 40 kilometers in one hour.
Non-Uniform Motion is when an object covers unequal distances in equal intervals of time. For instance, a bicycle moving through traffic may speed up, slow down, or stop, covering different distances in each time interval.
In uniform motion, the distance-time graph is a straight line, while in non-uniform motion, the graph is curved or jagged. These concepts help us understand how objects move consistently or unpredictably in different scenarios.

Q10: Describe the significance of measuring distances accurately in everyday life. Explain the concept of a ruler and its use in measuring lengths. Provide examples of situations where accurate distance measurement is important.
Ans: Accurate distance measurement is essential in our daily activities for various purposes:

• Ruler: A ruler is a common measuring tool used to measure lengths. It is usually marked with units like centimeters and millimeters.

Importance of Accurate Distance Measurement:

• Construction: Builders measure distances to ensure accurate building dimensions and alignment.
• Carpentry: Accurate measurements are crucial for cutting materials to specific sizes for furniture and structures.
• Education: Students use rulers to draw straight lines and measure lengths in geometry and other subjects.
• Crafts: Artists and crafters measure lengths to create precise designs and layouts.

A ruler helps us measure lengths accurately, ensuring that objects fit together, are aligned correctly, and meet specific requirements in various tasks.