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## Sunday 21 February 2021

### CBSE Class 11 Physics - MCQ and Online Tests - Unit 8 - Gravitation

#### CBSE Class 11 Physics – MCQ and Online Tests – Unit 8 – Gravitation

Every year CBSE schools conducts Annual Assessment exams for 6,7,8,9,11th standards. These exams are very competitive to all the students. So our website provides online tests for all the 6,7,8,9,11th standard’s subjects. These tests are also very effective and useful for those who preparing for any competitive exams like Olympiad etc. It can boost their preparation level and confidence level by attempting these chapter wise online tests.

These online tests are based on latest CBSE syllabus. While attempting these our students can identify the weak lessons and continuously practice those lessons for attaining high marks. It also helps to revise the NCERT textbooks thoroughly.

#### CBSE Class 11 Physics – MCQ and Online Tests – Unit 8 – Gravitation

Question 1.
There is no atmosphere on the moon because
(a) it is closer to the earth
(b) it revolves round the earth
(c) it gets light from the sun
(d) the escape velocity of gas molecules is less than their root mean square velocity here

Answer: (d) the escape velocity of gas molecules is less than their root mean square velocity here

Question 2.
The value of g at a particular point is 9.8 m/sec² suppose the earth suddenly shrink uniformly to half its present size without losing any mass. The value of g at the same point (assuming that the distance of the point from the centre of the earth does not shrink) will become
(a) 9.8 m/sec²
(b) 4.9 m/sec²
(c) 19.6 m/sec²
(d) 2.45 m/sec²

Question 3.
The time – period of a satellite of earth is 5 hours. If the separation between the earth and the satellite is increased to 4 times the previous value, the new time – period will become
(a) 10 hours
(b) 20 hours
(c) 40 hours
(d) 80 hours

Question 4.
A missile is launched with a velocity less than the escape velocity. The sum of its kinetic and potential energy is
(a) Positive
(b) Negative
(c) Zero
(d) may be positive or negative

Question 5.
What would be the duration of the year if the distance between the earth and the sun gets doubled?
(a) 1032 days
(b) 129 days
(c) 365 days
(d) 730 days

Question 6.
If a body of mass m is taken out from a point below the surface of earth equal to half the radius of earth, R, to a height R above the earths surface, then work done on it will be
(a) (5/6) mgR
(b) (6/7) mgR
(c) (7/8) mgR
(d) (8/9) mgR

Question 7.
A artificial satellite moving in a circular orbit around the earth has a total (kinetic + potential) energy E0. Its potential energy is
(a) 2E0
(b) E0
(c) 1.5 E0
(d) -E0

Question 8.
A body is projected vertically from the surface of the earth of radius R with velocity equal to half of the escape velocity. The maximum height reached by the body is
(a) R
(b) R/2
(c) R/3
(d) R/4

Question 9.
The escape velocity for a body projected vertically upwards from the surface of the earth is 11 km/s. If the body is projected at an angle of 450 with the vertical, the escape velocity will be
(a) 11/v2 km/s
(b) 11v2 km/s
(c) 2 km/s
(d) 11 km/s

Question 10.
If the distance between the earth and the sun were half its present value, the number of day in a year would have been
(a) 64.5
(b) 129
(c) 182.5
(d) 730

Question 11.
The masses of two planets are in the ratio 1 : 2. Their radii are in the ratio 1 : 2. The acceleration due to gravity on the planets are in the ratio.
(a) 1 : 2
(b) 2 : 1
(c) 3 : 5
(d) 5 : 3

Question 12.
The radius of the earth is 6400 km and g = 10 m/s². In order that a body of 5 kg weighs zero at the equator, the angular speed of the earth is

Question 13.
A body weighs 500 N on the surface of the earth. How much would it weight half way below the surface of the earth?
(a) 1000 N
(b) 500 N
(c) 250 N
(d) 125 N

Question 14.
A body is projected vertically from the surface of the earth of radius R with velocity equal to half of the escape velocity. The maximum height reached by the body is
(a) R
(b) R/2
(c) R/3
(d) R/4

Question 15.
The escape velocity of projection from the earth is approximately (R = 6400 km)
(a) 7 km/sec
(b) 112 km/sec
(c) 12.2 km/sec
(d) 1.1 km/sec

Question 16.
Who among the following first gave the experimental velocity of G?
(a) Cavendish
(b) Copernicus
(c) Brook Taylor
(d) none of these

Question 17.
A satellite S is move in an elliptical orbit around the earth. The mass of the satellite is very small compared to the mass of the earth .
(a) The acceleration of S is always directed towards the centre of the earth.
(b) The angular momentum of S about the centre of the earth changes in direction, but its magnitude remains constant.
(c) The total mechanical energy of S varies periodically with time.
(d) The linear momentum of S remains constant in magnitude.

Answer: (a) The acceleration of S is always directed towards the centre of the earth.

Question 18.
The mean radius of the earth is R, its angular speed on its own axis is w and the acceleration due to gravity at earths surface is g. The cube of the radius of the orbit of a geo-stationary satellite will be
(a) r²g / w
(b) R²w²/ g
(c) RG w²
(d) R²g / w²

Question 19.
A missile is launched with a velocity less than the escape velocity. The sum of its kinetic and potential energy is
(a) Positive
(b) Negative
(c) Zero
(d) may be positive or negative

Question 20.
If the radius of the earth were to be raise by 1% its mass remaining the same, the acceleration due to gravity on the surface of the earth will
(a) increase by 1%
(b) decrease by 2%
(c) decrease by 1%
(d) increase by 2%