# CBSE Class 7 Science Revision Notes Chapter 13

## CBSE Class 7 Science Revision Notes Chapter 13 – Motion and Time

Motion and Time Class 7 Science Chapter 13 Notes are concise and precise for students to get a deeper understanding of concepts such as different types of motion, speed, time, and distance. It covers various examples such as the working of a pendulum, devices used for measuring speed, etc. The notes can be easily accessed from the Extramarks’ website. Students can clarify any doubts they have about any topic of the chapter. Subject matter experts create these notes according to the CBSE guidelines. These notes will help students prepare the chapter well and save time by providing quick revisions of the chapter’s content.

## Revision Notes for CBSE Class 7 Science Chapter 13

### Motion

• The shifting of an object or the propensity of an object to move from its place over time is known as motion.
• An example of motion is the movement of the pendulum of a clock, etc.

### There are two types of motions

1. Uniform Motion: If a commodity moves in a linear line at a steady speed i.e., speed is fixed all the time, this motion is known as uniform motion.
2. Non-Uniform Motion: If a commodity moves in a straight line and the speed of an object keeps changing over time, the motion is called non-uniform motion.

### Speed

• The total distance covered by any object or article per unit of time is called speed.
• The basic or SI unit of speed is metres per second (m/s).
• Formula [Average Speed = Total distance covered / Total time taken].

### Measurement of Time

• The shadow of objects made by the sun was used to calculate time during ancient periods.
• A simple pendulum is a type of clock used to calculate time and it is the perfect case of periodic motion.
• The to-and-fro movement of an object is termed periodic or oscillatory motion.
• Oscillation is the process of an object moving back and forth.
• The time taken by the pendulum to finish one oscillation is considered the time period.
• The basic unit of time is denoted by the symbol “s” and its SI unit is seconds.

### Measuring Speed:

• Speedometer: It is a device used to evaluate the speed of a vehicle. It notes the speed in km/h.
• Odometer: It is a device used to calculate the distance travelled by a vehicle.

### Distance-Time Graph

• The motion of an object can be evaluated by a distance-time graph.
• The Y-axis represents the distance and the X-axis represents time.
• The distance-time graph is a linear line when the motion is uniform.
• If the speed of the object is increasing, the distance-time graph moves upwards.
• If the speed of an object is decreasing, the distance-time graph moves downwards.
• An object is considered to be stationary when the distance-time graph is lateral to the X-axis.
• An object’s speed is determined by the distance-time graph’s slope.
• The changing speed of an object signifies a curve in the distance-time graph.

### Class 7 Science Chapter Motion and Time Notes

Class 7 Science Chapter 13 Notes Motion and Time cover all the significant points of the topics in the chapter. These notes explain concepts, definitions, and terms using various examples and diagrams. Students can easily access these notes from the Extramarks website at their convenience. The Class 7 Science Notes for Chapter 13 are prepared to keep in mind the requirements of the students as well as the CBSE’s guidelines. These notes will be easy for students to refer to while preparing for exams.

### Time and Motion Class 7 Notes Revision

CBSE Class 7 Science Chapter 13 Motion and Time Notes are ideal for last-minute revisions. They explain the concepts of time, speed, distance, etc, that facilitate learning in students and help them gain an in-depth understanding of this topic.

### Motion

The complete path that is covered by an object in a particular time interval is termed distance. Displacement is the smallest distance an object covers in a particular time interval. Distance is measured after taking a product of speed and time. The distance is measured in metres and kilometres.

An object is said to be in motion if its position shifts over time. For example, when a car moves forward on the road. An object is considered to be at rest if it does not shift its position over time. For example, a person standing in one position on the ground.

As the unit of distance and time is metres and seconds respectively, the unit of speed in metres/second.

### The Types of Motion

Motion is categorised into three types. They are:-

• Rectilinear motion or translatory motion,
• Circular motion, and
• Period or oscillatory motion

Rectilinear or translatory motion is when the object or item moves in a straight line without shifting in its direction. For example, driving a car on a straight road.

A circular motion is where the object or item rotates in a circular shape at a fixed point and on a fixed radius. For example, the rotation of the planets around the sun.

A period or oscillatory motion is when the motion of an object or item repeats after a specified time interval. For example, the to and fro movement of the pendulum is one of the instances of oscillatory motion.

### The Oscillation of a Simple Pendulum

One complete oscillation is determined to be finished after the bob of the pendulum moves from A to B and later returns to A again. The total time taken by the pendulum to complete one oscillation is termed a time period.

### Time and Speed

Speed is calculated as the average speed of any object or body. Average speed is the entire distance that the object covers in a particular time interval. Speed is the entire distance travelled divided by the total time taken by an object. The basic unit of speed is calculated as in metres per second or kilometres per hour.

A motion can be either uniform or non-uniform. A uniform motion is considered to be when an object or body moves in a linear line, and with a steady speed. For example, a car moving in a linear line with constant speed. A non-uniform motion is when an object moves in a linear line, and its speed keeps modifying with time. For example, a moving train.

Time is generally calculated in seconds, hours, or minutes. The time period is the total amount of time needed by an object or body to finish one full oscillation.

### 1. Explain uniform and non-uniform motion.

If the speed of an object accelerates in a linear line and keeps changing, its motion is said to be non-uniform. On the other hand, if an object moves in a straight line with a constant speed, its motion is said to be uniform. It is rare to find objects in uniform motion.

### 2. What is the time period?

The time needed by the pendulum to finish one oscillation is known as its time period. For example, a pendulum has completed one oscillation after its bob (metallic ball) starts moving from its mean position O, moves to A, then to B, and returns to O. The pendulum also finishes one oscillation after its bob moves from one start position A to the other position B and returns to A.

### 3. What are the components of a simple pendulum?

A simple pendulum has components such as a small metallic ball or a piece of stone hanging from a firm stand by a thread. The metallic ball is termed the bob of the pendulum.

### 4. What is speed? How is the average speed calculated?

A higher speed signifies that a specified distance has been covered in a shorter time, or a longer distance covered in a particular time. The speed measured here is the average speed of a vehicle. Therefore, the average speed is the total distance covered divided by the total time taken.

Speed = Total distance covered/ Total time taken