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Chapter Analysis
Beginner16 pages • EnglishQuick Summary
The chapter 'Motion and Time' explores the concept of motion, types of motion including uniform and non-uniform motion, and the measurement of time and speed. It introduces devices like pendulums for measuring time and discusses tools such as speedometers for measuring speed. The concept of distance-time graphs is covered, demonstrating how they provide insight into objects' motion over time. The chapter emphasizes that speed is the distance covered per unit time, and discusses measurement units including seconds and meters/second for speed.
Key Topics
- •Speed and its units
- •Types of motion: uniform and non-uniform
- •Measurement of time with pendulums
- •Distance-time graphs
- •History of time measurement
- •Speedometer and odometer
- •Ancient time measuring devices
Learning Objectives
- ✓Understand the concept of speed and its measurement.
- ✓Differentiate between uniform and non-uniform motion.
- ✓Learn how to use and interpret distance-time graphs.
- ✓Explore the historical evolution of time measurement.
- ✓Understand the function of speedometers and odometers.
- ✓Familiarize with ancient methods for measuring time.
Questions in Chapter
Classify the following as motion along a straight line, circular or oscillatory motion: (i) Motion of your hands while running. (ii) Motion of a horse pulling a cart on a straight road. (iii) Motion of a child in a merry-go-round. (iv) Motion of a child on a see-saw. (v) Motion of the hammer of an electric bell. (vi) Motion of a train on a straight bridge.
Page 105
Which of the following are not correct? (i) The basic unit of time is second. (ii) Every object moves with a constant speed. (iii) Distances between two cities are measured in kilometres. (iv) The time period of a given pendulum is constant. (v) The speed of a train is expressed in m/h.
Page 105
A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?
Page 105
The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.
Page 105
The odometer of a car reads 57321.0 km when the clock shows the time 08:30 AM. What is the distance moved by the car, if at 08:50 AM, the odometer reading has changed to 57336.0 km? Calculate the speed of the car in km/min during this time. Express the speed in km/h also.
Page 106
Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s, calculate the distance between her house and the school.
Page 106
Additional Practice Questions
Explain how a distance-time graph helps in understanding motion.
mediumAnswer: A distance-time graph helps in understanding motion by showing the movement of an object over a period of time. A straight line indicates uniform motion while a curved line indicates non-uniform motion. The steepness of the line reflects the speed. It provides a visual way to easily understand and compare different motions.
What is the significance of Galileo's observation related to pendulums?
easyAnswer: Galileo observed that the time period of a pendulum is constant regardless of the amplitude of its swing, leading to the discovery of pendulum clocks. This principle of periodic time helped in measuring time accurately, revolutionizing time measurement.
Describe the experiment to measure the speed of a rolling ball.
mediumAnswer: To measure the speed of a rolling ball, draw a line on the ground and let a ball roll across it. Measure the time it takes for the ball to pass the line and the distance it travels from the line to when it comes to rest. Calculate the speed using the formula Speed = Distance / Time.
How can ancient devices such as sundials and water clocks be used to measure time?
mediumAnswer: Ancient devices like sundials and water clocks measure time based on the movement of the sun or the flow of water. Sundials use the position of a shadow cast by the sun to indicate the time of day, while water clocks measure time by the regulated flow of water from one container to another, marking specific intervals.
Why is it important to choose an appropriate scale when drawing a graph?
easyAnswer: Choosing an appropriate scale ensures that the graph accurately represents the data within the limits of the graph paper. It allows for clear representation and comparison of data points, ensures efficient use of space, and makes the graph easy to read and analyze.
NCERT Exemplar
AvailablePractice with NCERT Exemplar problems and solutions for this chapter. Exemplar problems are designed to help you master the concepts with advanced-level questions.
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