UPSC General Science: General Physics-2

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Today’s Topic: General Physics-1

1. A satellite S is moving 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 directed towards the centre of the earth.

b) The angular momentum of S about the earth changes in direction, but its magnitude remains constant.

c) Mechanical energy of S varies periodically with time.

d) The linear momentum of S remains constant in magnitude.

Ans:     A

Explanation:    Force on satellite is always towards earth, therefore acceleration of satellite S is always directed towards the center of the earth. Net torque of this gravitational force about center of the earth is zero. Therefore, the angular momentum of S about a centre of the earth is constant throughout.

2. Consider the following statements:

1) A geostationary satellite is at a height of 24,000km.

2) FM transmission of music is a very good quality is a very good quality because the atmospheric or man made noises which are generally frequencies variation can do little harm.

3) The geostationary satellite moves around the earth?

Which of the statements is/are correct?

a) 1and 3               b) 2 and 3               c) 1,2 and 3                d) 1 and 2

Ans:    B

Explanation:    A geostationary satellite is at a height of 36,000 km. It revolves around the around the earth from west to east in an orbit coplanar with equatorial plane. FM transmissible is quite immune to noise as AM transmission. Noise is an unwanted signal.

3. A converging lens is used to form an image on a screen when the upper half of the lens is covered by an opaque screen.

a) Half of the image will disappear b) Complete image will be formed

c) Intensity of the image will increase d) Intensity of the image will decrease

Choose correct options:

a) A and B               b) B and D               c) All of the above               d) B and C.

Ans:    B

Explanation:    When the upper half of the lens is covered, an image is formed by the rays coming from the lower half of the lens or image will be formed by less number of rays. Therefore, the intensity of image will decrease. But the complete image will be formed.

4. Match the following list:

A) High speed               1) Pascal

B) Pressure                   2) Joule

C) Energy                      3) Mach

D) Wavelength               4) Angstrom


A         B          C          D

a) 3          1          2          4

b) 1           2          3          4

c) 3          2          4          1

d) 2          4          1          3

Ans:     A


Quantity            Unit

High-speed        Mach

Pressure            Pascal

Energy               Joule

Wavelength       Angstrom

5. One astronomical unit is the average distance between:

a) Earth and the Sun               b) Jupiter and the Sun

c) Pluto and the Sun               d) None of these.

Ans:    A

Explanation:    One astronomical unit in the mean distance of earth from Sun. Its value is given

1AU = 1.5 x 1011 m

6. Which one of the following hormones regulated blood calcium and Phosphate:

a) Growth hormone               b) Thyroxine

c) Glucagon                          d) Parathyroid hormone.

Ans:     D

Explanation:    Parathyroid hormone controls the distribution of calcium and phosphates. Parathyroid hormone is important in bone development. Thyroxine – It faster the rate of cells respiration and essential for the normal growth of bones and hairs.

7. Consider the following statements: A simple pendulum is set into oscillation then:

1) The amplitude of oscillation of the simple pendulum decreases with time.

2) In each cycle the bob attain a given velocity twice.

3) Both acceleration and velocity of the bob zero when reach extreme position during the oscillation.

4) The acceleration is zero when the bob passes through the mean position.

Which are correct?

a) 1 and 2               b) 2 and 3               c) 2, 3 and 1                d) None of these.

Ans:     C

Explanation:    At the extreme position the acceleration will be maximum.

8. A car is running on a read at a uniform speed of 60km/h. The net resultant force on the car is:

a) Driving force in the direction of car’s motion b) Equal to zero

c) An incline force d) None of these

Ans:     C

Explanation:    The net resultant force on the car running on the road with a uniform velocity/speed is zero. Because at uniform speed acceleration of car is zero so the force is also zero. Force=Mass*Acceleration.

9. When the light waves pass from air to glass, the variable affected are:

a) Wavelength and velocity

b) Velocity and frequency

c) Wavelength and frequency

d) Wavelength, velocity, and frequency.

Ans:     A

Explanation:    The wavelength and frequency both are affected. Velocity decreases when it passes from rarer to denser medium. While the more a rare band in passing through a different medium the shorter will be wavelength. There is no effect on frequency on changing medium.

10. Which one of the following statements is not correct:

a) When the displacement of a body is zero then distance also zero.

b) When the acceleration of a particular is zero then resultant force on the particle is zero.

c) The velocity calculated by Distance/Time.

d) When the velocity of a particle is zero the momentum of it is also zero.