Table of Contents
Chapter 13- Motion and Time -Long Questions and Answers (Solved Worksheet)
Question 1- Explain the Difference Between Distance and Displacement
Answer-
- Definition of Distance and Displacement-
- Distance- It refers to the total path length covered during motion. For example, walking around a school playground along a specific path.
- Displacement- This is the shortest straight-line distance from the start point to the endpoint of the motion.
- Calculating Distance and Displacement-
- Distance Calculation- It is obtained by multiplying the speed with the time of travel. For instance, if a person walks at a speed of 5 m/s for 10 seconds, the distance covered is
- 5×10=50
- 5×10=50 metres.
- Displacement Calculation- It involves measuring the straight-line distance between the starting and ending points.
- Units of Measurement-
- Both distance and displacement are measured in metres (m) or kilometres (km).
- Key Differences-
- Displacement can be zero if the starting and ending points are the same, unlike distance which measures the entire path travelled.
- Displacement is a vector quantity (it has direction), while distance is a scalar quantity (no direction involved).
Also Check – Chapter 9 – Motion and Time – 4 Worksheets Solved and Unsolved
Question 2- Define Motion and Differentiate Between Objects in Motion and at Rest
Answer-
- Definition of Motion-
- Motion is when an object changes its position over time.
- Object in Motion-
- Meaning- An object is said to be in motion if it changes its position with respect to a reference point.
- Example- A car driving on a road, constantly changing its position.
- Object at Rest-
- Meaning- An object is at rest if it stays in the same place relative to a reference point.
- Example- Standing still in one spot on a playground.
- Understanding Through Observation-
- By observing an object’s position relative to its surroundings, one can determine if it’s in motion or at rest.
Question 3- Describe the Three Types of Motion and Provide Examples
Answer-
- Rectilinear/Translatory Motion-
- Characteristics- Movement in a straight line without turning or curving.
- Example- A car driving on a straight road.
- Circular Motion-
- Characteristics- Movement around a fixed centre point in a circular path.
- Example- Planets orbiting the sun.
- Periodic/Oscillatory Motion-
- Characteristics- Repetitive movement in a regular pattern back and forth.
- Example- The swinging of a simple pendulum.
Question 4- Explain the Concept of Speed and Its Measurement
Answer-
- Definition of Speed-
- Speed is the rate at which an object covers distance.
- Calculating Speed-
- Speed is calculated as the total distance covered divided by the total time taken.
- Formula- Speed = Total distance covered / Total time taken.
- Units of Speed-
- The basic unit is metres per second (m/s), but it can also be expressed in kilometres per hour (km/h) or metres per minute (m/min).
- Average Speed-
- This takes into account the total distance and total time, regardless of variations in speed during the journey.
- Measuring Speed-
- Instruments like odometers (measuring total distance travelled) and speedometers (indicating instantaneous speed) are used.
- Application in Calculations-
- For instance, if a vehicle travels 100 km in 2 hours, its average speed is
- 100 km/2 hours=50 km/h
- 100 km/2 hours=50 km/h.
Question 5- Contrast Non-uniform and Uniform Motion with Examples
Answer-
- Definitions-
- Non-uniform Motion- Occurs when an object’s speed changes over time. This can be due to acceleration, deceleration, or directional changes.
- Uniform Motion- Happens when an object moves at a constant speed, covering equal distances in equal time intervals.
- Examples-
- Non-uniform Motion Example- A car slowing down at a traffic light and then accelerating is an example of non-uniform motion, as its speed varies.
- Uniform Motion Example- A satellite orbiting Earth at a constant speed exhibits uniform motion, moving equal distances in equal time frames.
Question 6- Describe the Historical Methods of Time Measurement
Answer-
- Ancient Time Estimation Techniques-
- Observation of Shadows- People estimated time based on shadow length and direction, changing as the sun moved.
- Natural Events- Regular occurrences like sunrise marked new days, while lunar cycles defined months.
- Time Measurement Units-
- Day- Time from one sunrise to the next.
- Month- Based on the lunar cycle, from new moon to new moon.
- Year- The time it takes for Earth to orbit the Sun, marked by seasonal changes.
- Development of Short Interval Measurement-
- Innovations like sundials and water clocks emerged to measure shorter time intervals, preceding modern clocks.
Question 7- Explain the Structure and Motion of a Simple Pendulum
Answer-
- Pendulum Structure-
- Composition- Consists of a heavy object (bob) made of metal or stone.
- Suspension- The bob is attached to a stand via a lightweight, strong thread.
- Rest Position and Movement-
- Mean Position- At rest, the pendulum hangs straight down, known as the mean position.
- To and Fro Motion- When displaced and released, it exhibits ‘to and fro’ motion, swinging back and forth.
- Influence of Gravity-
- Gravity’s pull and momentum create the pendulum’s oscillatory motion.
Question 8- Discuss the Oscillatory Motion and Time Period of a Pendulum
Answer-
- One Oscillation-
- A complete movement from the start point, to one side, then the opposite side, and back constitutes one oscillation.
- Time Period-
- The time period is the duration of one complete oscillation.
- In an ideal scenario, this remains constant for each oscillation, provided the amplitude (maximum swing distance) is small.
Question 9- Explain the Units of Time and Their Relationships
Answer-
- Basic and Larger Units of Time-
- Second (s)- The fundamental unit of time.
- Minute (min)- Consists of 60 seconds.
- Hour (h)- Made up of 60 minutes.
- Practical Application-
- Time Calculations-
- Seconds in a Day- There are 86,400 seconds in a day (60 seconds/minute × 60 minutes/hour × 24 hours/day).
- Hours in a Year- Approximately 8,760 hours in a year (24 hours/day × 365 days/year).
- Time Calculations-
- Usage in Daily Life-
- Age Measurement- Typically expressed in years.
- Travel Time- Often conveyed in minutes or hours, not years.
Question 10- Describe the Units of Speed and How They Are Expressed
Answer-
- Basic Unit of Speed-
- Metre per Second (m/s)- Primary unit of speed, representing distance over time.
- Alternate Units of Speed-
- Metres per Minute (m/min)- Used for slower speeds.
- Kilometres per Hour (km/h)- Commonly used in vehicle speed.
- Writing Speed Units-
- Always written in singular form, e.g., ’50 km’, not ’50 kms’.
Question 11- Discuss the Perception and Measurement of Small and Large Time Intervals
Answer-
- Perception of Time-
- One Second Estimation- Saying “two thousand and one” aloud approximates one second.
- Heart Rate- Adult heart rate is around 72 beats/minute, while children are slightly higher.
- Measurement of Small Time Intervals-
- Common Clocks- Limited to measuring down to one second.
- Advanced Devices- Capable of measuring microseconds (one millionth of a second) and nanoseconds (one billionth of a second).
- Measurement of Large Time Intervals-
- Historical Time- Measured in centuries and millenniums.
- Astronomical Time- Ages of stars and planets measured in billions of years.
Question 12 – Explain the Different Types of Graphs and Their Uses
Answer-
- Bar Graph-
- Description- Uses rectangular bars to represent data, with the length/height indicating quantity.
- Usage- Ideal for comparing different items or categories, commonly used in media for its clarity.
- Pie Chart-
- Description- A circular graph divided into sectors, each representing a part of the whole.
- Usage- Best for showing how a total is divided into different portions, such as time spent on daily activities.
- Line Graph-
- Description- Connects data points with lines to show trends or patterns.
- Usage- Useful for illustrating changes over time, like tracking test scores across a school year.
Question 13- Explain How to Create and Interpret a Distance-Time Graph
Answer-
- Creating a Distance-Time Graph-
- Setting up Axes- Draw perpendicular x (horizontal) and y (vertical) axes on graph paper. The intersection is the origin.
- Assigning Quantities- Time on the x-axis, distance on the y-axis.
- Choosing Scales- Select scales that accurately represent the data (e.g., 1 minute = 1 cm, 1 km = 1 cm).
- Plotting Points- Mark points based on distance and time data.
- Drawing the Graph- Connect the points to illustrate the object’s motion.
- Interpreting the Graph-
- Slope- Represents speed; steeper slope means higher speed.
- Horizontal Line- Indicates the object is stationary.
- Straight vs. Curved Lines- Straight line suggests uniform motion; curved line indicates acceleration or deceleration.
Question 14- Provide a Practical Example of a Distance-Time Graph
Answer-
- Example Scenario-
- Data Points- A car’s movement data, e.g., 0 km at 0 minutes, 1 km at 1 minute, 2 km at 2 minutes, etc.
- Graph Result- Plotting these points will form a straight line, indicating constant speed.
- Analysis-
- Uniform Motion- The straight line shows the car is moving at a uniform speed.
- Speed Calculation- The slope of the line gives the car’s speed.
Question 15- Discuss Practical Applications and Experiments Related to Motion and Time
Answer-
- Experiments-
- Timing Pendulum Oscillations- Measure the time for a number of pendulum swings and calculate the average time period for one oscillation.
- Measuring Speed- Use speed formulas to calculate speeds of various objects, such as a rolling ball or a vehicle.
- Real-world Observations-
- Observing Vehicles- Compare speeds of different vehicles using odometer readings and time measurements.
- Personal Speed Measurement- Engage in activities like walking or cycling, measure the distance and time taken, and calculate your speed.
- Graphical Representation-
- Plotting Graphs- Create distance-time graphs for different motions to visually analyse speeds and motion types.
- Data Interpretation- Use the graph to estimate unmeasured distances and understand motion patterns.
Question 16- Analyse the Usefulness of Distance-Time Graphs in Understanding Motion
Answer-
- Comprehensive Motion Analysis-
- Speed Determination- Allows for the calculation of speed at any given time.
- Motion Patterns- Reveals whether the object’s speed is increasing, decreasing, or constant.
- Visual Representation-
- Enhanced Insight- A distance-time graph often provides more clarity than a table of values by showing the entire motion period.
- Application in Learning-
- Conceptual Understanding- The graphing exercise enhances theoretical knowledge with practical understanding.
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