Question: When is an object said to be in motion?
Answer: An object is said to be in motion when its position change with time in respect to a stationary object.
Question: Differentiate between rotatory motion and translatory motion.
Answer: Rotatory motion:
- Different parts of the body caver different distances is called rotatory motion.
- Eg: Moving fan and opening of a door.
- Different parts of the body cover equal distance in equal time is called translatory motion.
- Eg: Car running on road and walking.
Question: Name the two kinds of motion that the earth has.
Answer: When the earth rotation its axis which is rotational motion and when the earth revolves around the sun it is translatory motion, earth the motions are periodic motions.
Question: What is periodic motion. Explain with two examples.
Answer: The motion which repeat itself at regular intervals of time is called periodic motion. For Eg- rotation of the earth, pendull of a clock.
Question 1: Give two examples each of modes of transport used on land, water, and air.
Answer: Two examples of modes of transport used on land are buses and wheel carts.
Two examples of modes of transport used on water are ships and boats.
Two examples of modes of transport used in air are aeroplanes and helicopters.
Question: Fill in the blanks:
- One metre is ______________ cm.
- Five kilometres is ______________ m.
- Motion of a child on a swing is ______________.
- Motion of the needle of a sewing machine is ______________.
- Motion of wheel of a bicycle is______________.
- One metre is 100 cm.
- Five kilometres is 5000 m.
1 km = 1000 m
5 km = 1000 × 5 = 5000 m
Hence, the answer is 5000 m.
- Motion of a child on a swing is periodic.
The motion of a swing repeats itself at a certain time interval. Therefore, it has periodic motion. Hence, a child on a swing is said to have periodic motion.
- Motion of the needle of a sewing machine is periodic.
The needle of a sewing machine moves up and down repeatedly with a certain time interval. Hence, it is an example of periodic motion.
- Motion of the wheel of a bicycle is circular.
The central part of the wheel of a bicycle is attached to a fixed point. The wheel rotates about this fixed point as the bicycle moves. Hence, the wheel has circular motion.