Motion and Time Class 7 Notes
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Let us first look at the topics that we are going to study in this Chapter 13 Motion and Time of Class 7.
- What is Motion
- Types of Motion
- Slow and Fast Motion
- What is Speed
- What is Time
- Units of Speed and Time
- Time Measurement Instruments
- Simple Pendulum
- What is Oscillation, Time Period, and Amplitude?
- Distance-Time Graph
What is Motion or define motion?
When an object or a body changes its position with respect to time, the body or the object is said to be moving or it is said to be in motion.
Ex- If an object moves from Point A to Point B in a given time ‘t‘, then the object was moving in that time ‘t’ or was in motion in that time ‘t’.
Types of Motion
Motion can be of many types. Let us talk about some of the types of motion that are mentioned in the textbooks or we are going to study.
What is Rectilinear Motion?
It is a type of motion in which an object or a body travels in a straight line.
- It is also called Linear Motion and Straight Line Motion.
Example- Motion of a vehicle on a straight road.
What is Curvilinear Motion?
When a body or an object moves in a zig-zag or a curve path, it is said to be in a curvilinear motion.
Example- Motion of an object in a zig-zag path.
When an object moves in a circle is said to be in a circular motion.
Example- Motion of the moon around the earth
When an object rotates about an axis, the object is said to be in a rotational motion. Example- the rotation of the earth on its axis.
When a moving body covers equal distances in an equal interval of time, the body is said to be in a uniform motion.
- The speed of a body remains constant if it has a uniform motion.
When an object covers unequal distances in an equal interval of time, the body is said to be in a no-uniform motion.
- For a body having non-uniform motion, the speed keeps changing.
It is a type of motion that is repeated after a regular interval of time. Periodic Motion is also called oscillatory motion. Example- The swinging of the pendulum is an example of a periodic motion.
Slow and Fast Motion
Slow and Fast are relative terms.
An object is said to be moving faster than the other object if the first object takes lesser time to cover a fixed distance than the other object. Similarly, the first object is said to be moving slower than the other object if the first object takes more time to cover the fixed distance than the other object.
The object moving faster has a higher speed than the object moving slower.
What is Speed?
The speed of a body can be defined as the distance traveled by it in unit time.
Speed = Distance/time
- SI Unit of Speed is meter per second or m/s.
- The other unit of speed is- kilometer per hour or km/h.
- 45 km/h means the body can cover 45 km in one hour.
What is Average Speed?
It is the total distance traveled by the time taken
Odometer and Speedometer
What is a Speedometer?
A speedometer is a device or instrument used to measure the speed of a vehicle.
What is an Odometer?
An Odometer is a device or instrument used to calculate the total distance traveled by a vehicle.
What is time?
Time can be defined as an interval or duration of an event.
- The SI Unit of time is second (s).
- The other units of time are – minutes, hours, days, months, etc.
- Devices used to measure time- watches, clocks, Sundials, Sand-clock, etc.
The sundial measures the time by the position of the shadow cast by the sun.
It is one of the earliest devices used for measuring time by humans.
Sand Clock is also known by the name- hour-glass, sand-glass.
Sand Clock uses sand to measure time. It is made up of two glass bulbs separated by a narrow tube. The glass bulb is filled with a small amount of sand. When sand is passed from one bulb to the other it gives a constant time interval.
What is a Pendulum?
A simple pendulum consists of a metallic ball called a bob, suspended by a long thread from a fixed support. In a simple pendulum, the ball is free to swing about a fixed position (called the mean position).
Galileo Galilee was the first to study the motion of a simple pendulum.
What is oscillation?
The oscillation of a simple pendulum is a complete one-cycle (to and fro) of the bob of the pendulum.
What is the Time Period?
It is the time taken to complete one oscillation. The SI Unit of time period is second.
What is Amplitude?
Amplitude can be defined as the maximum displacement of the bob from its mean position (central position) to one of the extreme positions.
What is a distance-time graph?
The distance-time graph is a graphical representation of the distance traveled and the time taken.
Importance of Distance-Time Graph
What is the importance of a distance-time graph?
The distance-time graph helps us in many ways. It helps us to analyze the following-
- uniform and non-uniform motion
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