Chapter 1 Physical Environment Force Active Without Contact VSAQs
Question 1. What is the unit of G in SI and CGS units?
Answer:
The unit of G in SI and CGS units:-
The unit of G in the SI unit is N.m² /kg² and in the CGS unit is done.cm2/g²
Question 2. What is meant by gravitational force?
Answer:
Gravitational Force:-
Gravitational force is the force of attraction between any two point objects in this universe having masses “m,” and “m² ” separated by a distance “r”, acting along the line joining the objects and has the magnitude F-Gym² (where G is a constant known as the universal gravitational constant).
WBBSE Class 8 Force Active Without Contact very short answer questions
Question 3. The law of universal gravitation applies to two-point objects. Is this law valid for bigger objects (which obviously do not point objects)?
Answer:
Given:
The law of universal gravitation is applicable to two-point objects
If the distance between the two objects is much greater than the diameter of either of the objects, then the objects can be considered point masses.
Besides, the earth, moon, sun, stars, etc. have spherical shapes and their masses can be considered to be condensed at their geometric centre. So the law of universal gravitation can be directly applied.
Very short answer questions on non-contact forces for Class 8
Question 4. Why do raindrops fall on the earth?
Answer:
Raindrops fall on the earth because of
Earth pulls anything near its surface towards its centre by a force called gravity. So, everything near its surface, for example, raindrops, shredded leaves and fruits from a tree fall on the earth.
Question 5. What do you mean by acceleration due to gravity?
Answer:
Acceleration Due To Gravity:-
The acceleration produced in a freely falling object due to the earth’s gravity is called acceleration due to gravity.
Question 6. What is the magnitude of the acceleration due to gravity in an SI unit?
Answer:
The magnitude of the acceleration due to gravity in an SI unit
The acceleration due to gravity is 9.8 m/s² in the SI unit.
Read And Learn More WBBSE Solutions For Class 8 School Science Very Short Answer Type Questions
Question 7. Is “g” (acceleration due to gravity) a constant?
Answer:
No, “g” is not a constant. It depends on the distance from the centre of the earth.
Question 8. What is the magnitude of escape velocity on earth?
Answer:
The magnitude of escape velocity on earth
The magnitude of escape velocity on earth is 11.2 km/s.
WBBSE Chapter 1 quick answer solutions
Question 9. How far the Gravitational force exists between the two objects in this universe?
Answer:
The force of Gravitation is zero only when two objects are separated by an infinitely large distance. But in reality, beyond a certain distance, the force of Gravitation becomes negligibly small.
Question 10. What is the unit of charge in the SI unit?
Answer:
The unit of charge in the SI unit is the coulomb.
Question 11. When a glass rod is rubbed with a piece of silk what type of charges are generated on each of them?
Answer:
When a glass rod is rubbed with a piece of silk, the glass rod acquires a positive charge and the silk acquires a negative charge.
Question 12. When an ebonite rod is rubbed with a piece of wool what charges are generated on each of them?
Answer:
When an ebonite rod is rubbed with a piece of wool, the ebonite rod acquires a negative charge and the wool acquires a positive charge.
Question 13. Why an atom is electrically neutral (i.e. uncharged)?
Answer:
In an atom, the total number of positive charges is the same as the total number of negative charges. Hence, an atom has no net charge.
Question 14. What do you mean by static electricity?
Answer:
Static Electricity:-
When surfaces of two different objects are rubbed against each other, one of them may lose electrons and acquire a positive charge and the other gains the electrons and acquire a negative charge. The electricity so produced is called Static Electricity.
Question 15. The table to decide the nature of charges that develop due to rubbing is given here:
Answer:
| What kind of charges would develop if silk is rubbed with resin? |
| Silk |
| wood |
| Human body |
| Resin |
| Celluloid |
| Silk- Positive charge |
| Resin- Negative Charge |
Question 16. Name the device which is used to detect the presence of static charge in a body.
Answer:
Electroscope
WBBSE Class 8 Science very short answer practice
Question 17. Why does a sheet of paper fall slower than one that is crumpled into a ball?
Answer:
When the sheet of paper is crumpled into a ball, its density increase (due to a decrease in volume) and hence, resistance to its motion through air decreases. Thus it falls faster than a sheet of paper.
Question 18. Which force is responsible for the revolution of planets around the sun?
Answer:
Gravitational force of attraction between the sun and the planets.
Question 19. A man can lift an object of mass 10 kg on the surface of the earth. What will be the maximum mass which he can lift at the surface of the moon by applying the same muscular force?
Answer:
10 kg x 6 = 60 kg
WBBSE Class 8 Science revision very short answers
Question 20. Two bodies attract each other with a force F in the air. What will be the value of the force when the same bodies are immersed in water?
Answer:
The force of gravitation does not depend on the intervening medium. Hence the force shall remain as F.