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# 1st Year Physics Chapter 1 Short Questions Notes PDF

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In this post, I am sharing FSc 1st Year Physics Chapter 1 Short Questions with Answers Notes PDF for the students of Intermediate Part 1. This is the 1st chapter in the class 11 Physics textbook and its name is Measurements. From this post of ilmihub, students can download the 11th class chapter 1 Measurements short questions notes in PDF format on their laptops or mobiles. These Class 11 Physics Chapter 1 Short Questions with Answers Notes are for all the boards working under the Punjab Board like Gujranwala Board, Lahore Board, Faisalabad Board, Multan Board, Rawalpindi Board, Sargodha Board, DG Kahn Board, and Sahiwal Board. Here are the complete FSC 1st Year Physics Notes PDF of all chapters.

## Class 11 Physics Chapter 1 Measurements Short Questions with Answers

### Name several repetitive phenomena occurring in nature, which could serve as reasonable time standards.

Any natural phenomenon that repeats itself after exactly the same interval of time can be used for the measurement of time. The measurement is based on the counting of its repetitions.
Some natural phenomena are:
1)  Rotation of the earth about its axis which determines the length of the day
2) Change of shadow of an object in the light of the sun.
3) The rotation of the planets in the solar system.

### Give the drawbacks to using the period of the pendulum as a time standard.

The period of the simple pendulum is given by:
T = 2p√l/g
The relation shows that the time period of a simple pendulum depends upon its length “l” and the value of “g” at any place.

• As the value of gravitational acceleration “g” changes at different places, so it will change the time period of the pendulum.
• Due to changes in temperature, the length “l” of the pendulum will change. Thus the time period will also change.
• Surrounding atmosphere or air resistance may affect the time period of the simple pendulum.

In the light of above drawbacks, the time period of the pendulum cannot be used as the time standard.

The radian is the plane angle between two radii of a circle which cut off on the circumference an arc, equal in length to the radius of the circle. The total plane angle of a circle is 2p rad.

The steradian is the solid angle (three-dimensional angle) subtended at the centre of a sphere by an area of its surface equal to the square of the radius of the sphere. The total solid angle for a sphere is 4p sr.