Chapter-05: Gravitation

After studying this unit, the students will be able to:

• State Newton's law of gravitation.
• Explain that the gravitational forces are consistent with Newton's third law.
• Explain gravitational field as an example of field of force.
• Define weight (as the force on an object due to gravitational field).
• Calculate the mass of Earth by using law of gravitation.
• Solve problems using Newton's of gravitation.
• Explain that value of g decreases with altitude from the surface of earth.
• Discuss the importance of Newton's law of gravitation in understanding the motion of satelittes.

Multiple Choice Questions
1.	_______ predicted about artificial satellites about 300 years ago.
	a. Galileo	b. Newton
	c. Einstein	d. Faraday
2.	Unit of gravitational field strength is:
	a. N	b. N kg-1
	c. J	d. N m
3.	Distance of moon from Earth is?
	a. 38,000 km	b. 380,000 km
	c. 3,000,000 km	d. 30,000 km
4.	Speed of GPS satellite is:
	a. 7.9 kms	b. 3.87 kms-1
	c. 5.6 kms-1	d. 5.0 kms-1
5.	If the distance between two masses is half then the force of gravitation becomes:
	a. One fourth	b. Four times
	c. Doubled	d. Half
6.	In System International, the value of G is:
	a. 6.4 x 106 Nm2kg-2	b. 6.4 x 10-11 Nm2kg-2
	c. 6.67 x 1011 Nm2kg-2	d. 6.67 x 10-11 Nm2kg-2
7.	Radius of earth is:
	a. 6.4 x 106 km	b. 6.4 x 106 m
	c. 6 x 106 m	d. 6 x 106 km
8.	The SI unit of gravitational force is:
	a. Nm2kg-2	b. Newton
	c. ms-2	d. both a & b
9.	What will be the value of G if mass of the earth becomes four times:
	a. No change	b. Four times
	c. One fourth	d. Doubled
10.	The mass of Earth is approximately:
	a. 6.9 x 1024 kg	b. 6.0 x 10-24 kg
	c. 6.0 x 1024 kg	D. 5500 x 1024 kg
11.	As we go up the value of G becomes:
	a. Unchanged	b. Increases
	c. Decreases	d. Doubled
12.	The force which pulls the object towards the center of circle is known as ______ force:
	a. Frictional	b. Coulomb
	c. Centripetal	d. Gravitational
13.	When an object is at a height equal to radius of earth above the surface of the earth. What is the value of gh?
	a. 4g	b. 2g
	c. g/2	d. g/4
14.	14. What is not true about g?
	a. g is different at different places	b. g is greater at poles
	c. g is less at poles	d. g decreases as go higher
15.	If the weight of an object on the surface of earth is W. Its weight on the surface of moon will be:
	a. 6W	b. W/6
	c. W/4	d. W/8
16.	On mountains our weight will be ______ as compared to weight on the surface of earth.
	a. Equal	b. Greater
	c. Less	d. None of above
17.	If mass of both the bodies is 1kg and distance between their centers is lm then the gravitational force will be equal to:
	a. G	b. g
	c. V	d. None of above
18.	An artificial satellite keeps on revolving around the earth in different orbits with uniform speed due to the?
	a. Gravitational force	b. Frictional force
	c. Coulomb force	d. Electromagnetic force
19.	Relative velocity of Geostationary satellite with respect to earth is:
	a. 7.9 kms-1	b. 11.2 kms-1
	c. 9.8 ms-1	d. Zero
20.	If a rocket is fired vertically with a speed of _______, it will start revolving around the earth:
	a. 8 ms	b. 8 kms-1
	c. 9.8 ms	d. 11.2 kms-1
21.	Height of the Geostationary satellite above the surface of earth is:
	a. 1000 km	b. 3600 km
	c. 36000 km	d. 42300 km
22.	Gravitational force on the surface of earth is equal to:
	a. G	b. g
	c. W	d. All of above
23.	Weight of the body of mass 10 kg on the surface of moon:
	a. 160 N	b. 16N
	c. 1.62 N	d. None of above

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