Important Notes for CBSE Class 7 Science Chapter 13 – Motion and Time. Motion and Time Class 7 Notes and Study Material Download in PDF form.
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Motion and Time Class 7 Notes
Motion can either be in a straight line or circular motion or it may also have periodic motion.
An object can have either slow motion or may have a fast motion.
To understand if an object is moving slowly or fast the distance and time is used.
- SPEED:
1.) Speed of an object is determined by distance and time.
2.) Average speed is usually calculated using total distance covered divided by the total time.
3.) Non- uniform motion: if motion along the same line keeps changing it is called as non-uniform motion
4.) Uniform motion: if the objects move in a straight line, it is called as uniform motion.
Measurement of time:
- In olden time, time was calculated with the position of the from sunrise to sunset.
- Time between 2 consecutive sun rises is called a day.
- A month is a period between one new moon to the next.
- A year is calculated as the time taken by the art to complete one revolution around the sun
- Watches, clocks make use of periodic motion to calculate the time. e.g., simple pendulums.
- Simple pendulum: It is made up of a metallic ball or stone attached to a thread.
- Bob: it is a metal ball in a pendulum.
- The pendulum is example of oscillatory or periodic motion.
- Time period: The time taken to complete one oscillation.
UNIT OF TIME AND SPEED:
1.) Time is measured in seconds, minutes and hours
2.) The unit of speed is meter per minute or kilometer per hour.
3.) Unit is always measured as a singular unit.
4.) Sundials, water clocks and sand clocks are also used.
MEASURING SPEED:
- The speed of an object, you can find the distance moved by it in a unit time.
- Speedometer is used to measure speed.
- Odometer is used to measure speed of vehicles.
DISTANCE-TIME GRAPH:
- A bar graph, pie chart, line graph can be used to describe distance-time graph.
- Graph can be drawn on graph paper or on a computer.
- This graph provides information about the type of motion.