Question

time chapter questions​

Answer 1

Answer:

12. Time: Any change or movement which takes place, is understood in terms of physical dimensions called time.

13. Periodic events: Events which repeat themselves over a regular / fixed interval of time are called periodic events.

Ex:  Sunrise, sunset, changes in the appearance of moon.

14. Name them:

a. The time interval between one sunrise and the next is day

b. The time interval between one new moon and the next is month

c. The time taken by the earth to complete one revolution of sun is year

15. Measurement of time:

a. Devices used to measure time during early days:  sundial, the hour glass, water clock.

b. Devices used to measure time now: clocks, watches, stop clocks

c. Quartz clocks having suitable circuits in them help us calculate the time more precisely.

16.  Simple pendulum:

a. A simple pendulum is made up of a metal ball (bob) attached to a taut light string or thread, that is fixed rigidly at one end.

b. The bob is free to oscillate. When a pendulum is at rest, the bob is in its mean (equilibrium) position.

c. When the bob is slightly displaced, it undergoes to and fro motion.

d. One oscillation gets completed when the pendulum goes from one extreme(initial) position  to its mean position, then to the other extreme

position , again to its mean position and again finally back to its initial (extreme) position.

Draw on the white plain page

17. Time period: The time taken by the pendulum to complete its one oscillation is called as the time period of the pendulum.

Time period =     Time taken  

                          Number of oscillations

18.  Time period of the pendulum:

a. A slight change in initial displacement does not affect the time period of the pendulum

b. A pendulum of given length takes a definite time to complete one oscillation. ie. If the pendulums are of same length, their time periods   are same.

19.  Copy Activity3 from text book.

Inferences: a. Is the average speed during its full length roll equal to the average speed when it rolls from half way down the inclined plane?

Ans:  The average speed of the ball decreases when it rolls from half way down the inclined plane.

c. What happens to the average speed if angle of inclination of the plane is changed?

Ans: the average speed increases as the angle of inclination of the plane increases.

Explanation: