Question

B. LONG ANSWER TYPE QUESTIONS
1. Why do we need standard units for measurement ?
2. Mention the precautions to be observed while measuring the length of a pencil using a ruler.
3. When an object is said to be in motion ?
4. Define circular motion. Give one example also.
5. Describe periodic and non-periodic motion with suitable example.
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Answer 1

Answer:

4) Circular motion is simply defined as "The motion of the object which moves in the circular form is called as circular motion"

ex:pedaling a cycle

Answer 2

Answer:

1) A standard unit of measurement is a quantifiable language that helps everyone understand the association of the object with the measurement. Although measurement is an important part of everyday life, kids don't automatically understand the different ways to measure things.

2) i)the level of eye and level of scale mark should be perpendicular to each other.

ii) the zero of scale should coincide with starting point.

iii) it should be straight along the line.

3) a object is said to be in motion when it moves from one place to another with respect to its surrounding. An object is said to be in motion if it changes its position with time,with respect to its surroundings.

4)Examples of circular motion include: an artificial satellite orbiting the Earth at a constant height, a ceiling fan's blades rotating around a hub, a stone which is tied to a rope and is being swung in circles, a car turning through a curve in a race track, an electron moving perpendicular to a uniform magnetic field, ...

5) Periodic motion: A motion which gets repeated after regular intervals of time is called a periodic motion.

Examples : The earth moving around the sun taken 365 days to complete one revolution and this motion gets repeated after every 365 days.

Non-periodic motion : The motion which does not repeat itself after regular interval of time is called non-periodic motion.

Examples : A footballer running on a field, application of brakes in a moving vehicle , a ball rolling the ground gradually slows down finally stops, motion of tides in the sea, etc.