This PSEB 7th Class Science Notes Chapter 13 Motion and Time will help you in revision during exams.
PSEB 7th Class Science Notes Chapter 13 Motion and Time
→ If an object does not change its position with respect to the objects around it and with time, then that object is called at rest.
→ If an object changes its position according to the objects around it and with time, then it is in motion.
→ The motion in a straight line of an object is called straight-line motion.
→ The motion of an object on a circular path is called circular motion.
→ If an object moves around its center position, the motion of that object is called Periodic motion.
→ If an object takes very little time to cover a short distance then the speed of the object is fast and if the object takes more time to cover the same distance then its speed is called slow.
→ The distance covered in 1 unit time is called the Speed. Its S.I. unit is meter per sec (m/s).
→ The Speed can be calculated using the following formula: ccc
→ The motion of an object moving at a speed along a straight line is called a Uniform Motion when the motion of an object moving at different speeds on a straight line is called Non-uniform Motion.
→ The motion of the hour hand of the clock, the motion of the earth around the sun, and the motion of a simple pendulum all are examples of uniform motion.
→ Nowadays we measure time with wall clocks, table clocks, wristwatches, or mobile phones. The SI unit of time in seconds.
→ Heavy mass (metal sphere) tied to a thread and hung in a fixed place or stand is called a simple pendulum.
→ The movement of a simple pendulum back and forth a point is called a recurring or oscillating motion.
→ The time taken to complete one oscillation is called the time period.
→ The number of oscillations completed in a second is called frequency. The S.I. unit of frequency is hertz.
→ A device that measures the speed of vehicles is called a Speedometer.
→ The speedometer measures the speed of vehicles in kilometers/hour.
→ An instrument used to measure the distance covered by vehicles is called an Odometer.
→ The graph illustrates the comparison of one quantity with another.
→ There are generally three types of graphs prevalent:
- Linear graph
- Bar graph
- Pie chart
→ The distance-time graph is a linear graph.
→ It represents the graph between the distance and time covered by the object.
→ The amount that is independent is represented on X-axis (horizontal axis) and the other amount which is dependent is on the Y-axis (vertical axis).
→ If an object is at rest, its distance-time graph is a straight line parallel to the X-axis.
→ Graph: If two quantities depend on each other then their representation is called a graph.
→ Speed: The distance covered by the object in the unit time interval is called the speed.
→ Uniform motion: When an object travels equal distances in equal time intervals, the motion is uniform.
→ Non-uniform motion: The motion of an object when it does not cover the same distance in equal time intervals is called non-uniform-motion.
→ Simple pendulum: A small piece of metal or stone hanging with the help of thread from a fixed point is called a simple pendulum.
→ Oscillation: When a freely hanging object moves from its center position to one extreme side and then to the other extreme side and finally reaches its previous position i.e. middle position, the object is said to complete an oscillation.
→ Time period: The time taken by a simple pendulum to complete an oscillation is called a time period.
→ Uniform speed: When an object travels equal distances in equal time intervals, no matter how small the time interval, the speed of the object is called uniform speed.
→ Non-uniform speed: When an object does not cover equal distances in equal time intervals, no matter how short the time interval, the speed of that object is called non-uniform speed.