RBSE Solutions for Class 8 Science Chapter 15 Some Natural Phenomena

Rajasthan Board RBSE Solutions for Class 8 Science Chapter 15 Some Natural Phenomena Textbook Exercise Questions and Answers.

RBSE Class 8 Science Solutions Chapter 15 Some Natural Phenomena

RBSE Class 8 Science Some Natural Phenomena InText Questions and Answers

Page 184

Question 1. 
I wonder why they took so many years to realise the similarity.
Answer:
Because it is a scientific invention and the scientific inventions are the result of long time hard work of many people.

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Question 2. 
My grandmother told me that the earth is balanced on the horn of a bull and when the bull shifts it to the other horn, an earthquake takes place. How could it be true?
Answer:
In ancient times, people were unaware of the true facts of most of the events that takes place in nature like stroms, earthquakes, etc. therefore, they expressed mythical stories.

Question 3. 
What could cause a disturbance inside the earth?
Answer:

1. Most of the earthquakes are caused by the movements of the earth's plate.
2. Earthquake also occurs due to volcanic eruptions.
3. Earthquake can also occur due to a meteorite hitting the earth.
4. Underground nuclear explosion can also give rise to earthquake.

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Question 4. 
If scientists know so much about earthquakes, can they also predict when and where the next one will strike?
Answer:
No, it has not been possible for the scientists to forecast the exact time and place for the earthquake.

RBSE Class 8 Science Some Natural Phenomena Textbook Questions and Answers   

Select the correct option in Question 1 and 2.

Question 1. 
Which of the following can not be charged easily by friction?
(a) A plastic scale 
(b) A copper rod 
(c) An inflated balloon 
(d) A woollen cloth 
Answer:
(b) A copper rod 

Question 2. 
When a glass rod is rubbed with a piece of silk cloth the rod
(a) and die cloth both acquire positive charge.
(b) becomes positively charged while the cloth has a negative charge.
(c) and the cloth both acquire negative charge.
(d) becomes negatively charged while the cloth has a positive charge.
Answer:
(b) becomes positively charged while the cloth has a negative charge.

Question 3. 
Write T against true and F against false in the following statements :
(a) Like charges attract each other (T/F)
(b) A charged glass rod attract a charged plastic straw (T/F)
(c) Lightning conductor cannot protect a building from lightning (T/F)
(d) Earthquakes can be predicted in advance (T/F)
Answer:
(a) F 
(b) T
(c) F 
(d) F 

Question 4. 
Sometimes a crackling sound is heard while taking off sweater during winters. Explain.
Answer:
While taking off the sweater, it becomes charged due to friction. When these charges come in contact due to their attraction or repulsion, a 'cracking' sound is produced.

Question 5. 
Explain why a charged body loses its charge if we touch it with our hand.
Answer:
Human body is a conductor of electricity. When we touch any charged body by our hand, the charge through our body goes into the earth and the body loses its charges.

Question 6. 
Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?
Answer:
The scale on which the destruction power of earthquake is measured is called 'Richter Scale'. Yes, the measure of 3 can be taken on Richter scale using seismograph but this earthquake is very weak and won’t cause much destruction. 

Question 7. 
Suggest three measures to protect ourselves from lightning.
Answer:

1. As soon as thunder is heard, one must move into a house or a building.
2. If you are travelling in a car or bus, close the doors and windows. You will be safe inside a closed conductor.
3. If you are in an open ground where no covered shelter is present, then stand away from trees. Don’t lie down on the floor, instead squat low on the floor. Put your hands on your knees, with your head between the hands. This position will make you smallest target to be struck.

Question 8. 
Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
Answer:
Like charges repel each other while unlike charges attract each other. That is why balloons with like charges repel each other and a charged and an uncharged balloon due to their different nature attract each other.

Question 9. 
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Answer:
A charged object can be detected by an instrument known as Electroscope. 
Electroscope: 
In an electroscope, firstly there is a metal rod whose one end has a metal disk attached. The other end has two metal foils. These foils are enclosed in a glass jar. If any uncharged object is brought in contact with the metal rod of electroscope, then there is no divergence in metal foils. On the other hand, if any charged object is brought in contact, then the diverge. On removing the charged object, the foils remain diverged.

Question 10. 
List three states in India where earthquakes are more likely to strike. 
Answer:
States where earthquakes are most probable:

• Kashmir 
• Gujarat (Rann of Kutch)
• Rajasthan

Question 11. 
Suppose you are outside your home and an earthquake strikes. What precautions would you take to protect yourself?
Answer:

1. One must move to an open area, away from buildings, trees and electricity poles and lie down on the ground.
2. If you are in a car or bus, do not step out.
3. Take the car or bus to an open area.
4. Don't move out until shaking of earth stops. 

Question 12. 
The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella ? Explain.
Answer:
Lightning can attack on telephone wires, electricity wires, metal pipes and black coloured objects. We must not touch them during thunder - storm. Therefore, during a thunder - storm, one must not carry an umbrella, because its generally made up of a black cloth and also has iron rods, that are good conductor of electricity.