NCERT Solutions Class 9 Science Chapter 10

NCERT Solutions Class 9 Science Chapter 10 Gravitation answers of intext questions given on Page 134 or Page 136 or Page 138 or Page 141 or Page 142 or Exercises in English Medium updated for new academic session 2020-21.

Download Class 9 Science chapter 10 in Hindi Medium also. You can download पेज 149 के उत्तर or पेज 152 के उत्तर or पेज 153 के उत्तर or पेज 157 के उत्तर or पेज 158 के उत्तर or अभ्यास के प्रश्न उत्तर in Hindi Medium free to use. NCERT Solutions Apps 2020-21 for class IX are also available for download free based on latest CBSE Syllabus 2020-2021.

NCERT Solutions Class 9 Science Chapter 10

Class:9
Subject:Science – विज्ञान
Chapter 10:Gravitation

9th Science Chapter 10 Answers in English & Hindi Medium

NCERT Solutions Class 9 Science Chapter 10 Gravitation Intext Questions and Exercise questions are given below in Hindi and English Medium updated for session 2020-21. Solutions are based on latest CBSE Books 2020-21 based on new CBSE Syllabus 2020-2021.

A particular is dropped from a tower 180 m high. How long does it take to reach the ground? What is the velocity when it touches the ground?

Take g = 10 m/s².
Answer:
6 s, 60 m/s

How much would a 70 kg man weigh on moon? What will be his miss mass on earth and moon? Given g on moon = 1∙7 m/s².

119 N, 70 kg, 70 kg

Calculate the value of acceleration due to gravity on Moon. Give n mass of moon = 7.4 x 10²² kg, radius of moon = 1740 km.

1.63 m/s²

A car weighs 1200 kg. This weight is evenly distributed on 4 wheels. If the pressure in each Tyre is 15 kg wf/cm², what is the area of each Tyre in contact.

20 cm²

Why are sleeper used below the rails?

Sleeper are placed below the rails to increase area (A) and to consequently decrease pressure (P) due to weight (W) of a train on the rails as P= F/A = W/A (∙.∙ F = W). This prevents the railways line from sinking into ground.

The mass of a block made of certain material is 13.5 kg and its volume is 15 x 10-³ m³. Will the block float or sink in water? Give reason for your answer.

The block floats.

Relative density of silver is 10.8. The density of water is 10³ kg/m³. What is the density of silver in SI units?

10.8 x 10³ kg/m³

Questions for Practice on 9th Science Chapter 10

Question 1:
A boy weighing 60 kg f is wearing shoes with heel area of cross-section 20 cm² while a girl weighing 45 kg f wearing shoes with heel of area of cross-section 1.5 cm². Compare the pressure exerted on ground by their heels when they stand on the heel of one foot.
Answer 1:
The girl’s shoe heel exerts a pressure 10 times more than the boy’s shoes heel.

Question 2:
A car falls off a ledge and drops to the ground in 0.5 s. Let g = 10 m/s² (for simplifying the calculations).
(a) What is its speed on striking the ground?
(b) What is its average speed during 0.5 s?
(c) How high is the ledge from the ground?
Answer 2:
(a) 5 m/s (b) 2.5 m/s (c) 1.25 m

Question 3:
A block of wood is kept on a table top. The mass of the wooden block is 5 kg and its dimensions are 40 cm x 20 cm x 10 cm. Find the pressure exerted by the wooden block on the table top if it is made to lie on the table with its sides of dimensions (a) 20 cm x 10 cm (b) 40 cm x 20 cm. given g = 9.8 m/s².
Answer 3:
(a) 2450 Pa (b) 612.5 Pa

Important Questions on 9th Science Chapter 10

गुरुत्वाकर्षण का सार्वत्रिक नियम बताइए।
गुरुत्वाकर्षण का सार्वत्रिक नियम: “विश्व का प्रत्येक पिंड प्रत्येक अन्य पिंड को एक बल से आकर्षित करता है, जो दोनों पिंडों के द्रव्यमानों के गुणनफल के समानुपाती तथा उनके बीच की दूरी के वर्ग के व्युत्क्रमानुपाती होता है। यह बल दोनों पिंडों को मिलाने वाली रेखा की दिशा में लगता है।“
Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?
All objects fall on ground with constant acceleration, called acceleration due to gravity (in the absence of air resistances). It is constant and does not depend upon the mass of an object. Hence, heavy objects do not fall faster than light objects.
The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why?
According to the universal law of gravitation, two objects attract each other with equal force, but in opposite directions. The Earth attracts the moon with an equal force with which the moon attracts the earth.
मुक्त पतन से आप क्या समझते हैं?
जब वस्तुएँ पृथ्वी की ओर केवल गुरुत्वीय आकर्षण बल के कारण गिरती हैं तो इसे मुक्त पतन कहते हैं। इस समय वस्तु का त्वरण (g=9.8 ms^(-2) ) गुरुत्वीय त्वरण के बराबर होता है।
गुरुत्वीय त्वरण से आप क्या समझते हैं?
मुक्त पतन के दौरान गिरते हुए पिंड पर पृथ्वी के गुरुत्वीय बल के कारण जो त्वरण उत्पन्न होता है उसे गुरत्वीय त्वरण कहते हैं। पृथ्वी पर इसका मान लगभग 9.8 ms^(-2) होता है।
If the moon attracts the earth, why does the earth not move towards the moon?
The Earth and the moon experience equal gravitational forces from each other. However, the mass of the Earth is much larger than the mass of the moon. Hence, it accelerates at a rate lesser than the acceleration rate of the moon towards the Earth. For this reason, the Earth does not move towards the moon.
What is the importance of universal law of gravitation?
The universal law of gravitation proves that every object in the universe attracts every other object.
What do we call the gravitational force between the Earth and an object?
Gravitational force between the earth and an object is known as the weight of the object.
किसी वस्तु का चंद्रमा पर भार पृथ्वी पर इसके भार का 1/6 गुना क्यों होता है?
वस्तु का भार (W = mg) गुरुत्वीय त्वरण (g) के मान पर निर्भर करता है। चंद्रमा पर गुरुत्वीय त्वरण का मान पृथ्वी पर गुरुत्वीय त्वरण के मान का 1/6 गुना होता है। इसलिए चंद्रमा पर वस्तु का भार, पृथ्वी के भार का 1/6 गुना होता है।
Why will a sheet of paper fall slower than one that is crumpled into a ball?
When a sheet of paper is crumbled into a ball, then its density increases. Hence, resistance to its motion through the air decreases and it falls faster than the sheet of paper.
In what direction does the buoyant force on an object immersed in a liquid act?
An object immersed in a liquid experiences buoyant force in the upward direction.
Why does a block of plastic released under water come up to the surface of water?
Two forces act on an object immersed in water. One is the gravitational force, which pulls the object downwards, and the other is the buoyant force, which pushes the object upwards. If the upward buoyant force is greater than the downward gravitational force, then the object comes up to the surface of the water as soon as it is released within water. Due to this reason, a block of plastic released under water comes up to the surface of the water.
एक पतली तथा मजबूत डोरी से बने पट्टे की सहायता से स्कूल बैग को उठाना कठिन होता है, क्यों?
पतली डोरी से बने पट्टे से स्कूल बैग का भार (लगने वाला बल) कंधे के कम क्षेत्रफल पर पड़ता है, जिससे कंधे पर अधिक दबाव पड़ता है और बैग उठाने में कठिनाई होती है।
उत्प्लावकता से आप क्या समझते हैं?
जब किसी वस्तु को किसी तरल में डुबाते हैं तो तरल द्वारा वस्तु पर ऊपर की ओर एक बल लगाया जाता है, जिसे उत्प्लावन बल कहते हैं तथा इस क्रिया को उत्प्लावकता कहते हैं।
पानी की सतह पर रखने पर कोई वस्तु क्यों तैरती या डूबती है?
यदि वस्तु का घनत्व पानी के घनत्व से कम है या बराबर है तो वस्तु पानी पर तैरती रहेगी अन्यथा वस्तु पानी में डूब जाएगी।
या
यदि वस्तु का भार उसके द्वारा विस्थापित जल के भार से कम या बराबर है तो वस्तु पानी में तैरेगी अन्यथा डूब जाएगी।
आपके पास एक रुई का बोरा तथा एक लोहे की छड़ है। तुला पर मापने पर दोनों 100 kg द्रव्यमान दर्शाते हैं। वास्तविकता में एक-दूसरे से भारी है। क्या आप बता सकते हैं की कौन-सा भारी है और क्यों?
रुई का बोरा वास्तविकता में अधिक भारी है। रुई के बोरे का क्षेत्रफल लोहे की छड़ से अधिक है इसलिए रुई के बोरे पर अधिक उत्प्लावन बल लगेगा जो उसके वास्तविक भार को कम दिखाएगा।

NCERT Solutions Class 9 Science Chapter 10 Gravitation Intext Questions on page 134
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NCERT Solutions Class 9 Science Chapter 10 Gravitation Intext Questions on page 138
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