Physics (Part-2) (CDS-Solved Paper)

Total Questions: 50

21. A myopic person has a power of −125. D. What is the focal length and nature of his lens? [Morning Shift-2016 (I)]

Correct Answer: (d) − 80 cm and concave lens
Solution:

22. Which one of the following statements about bar magnet is correct? [Morning Shift-2016 (I)]

Correct Answer: (c) When a piece of bar magnet is bisected perpendicular to its axis, two new bar magnets are formed.
Solution:

Bar magnet has equal and opposite magnitude at their poles. When a bar magnet is bisected perpendicular to its axis, it always create a new bar magnet. The poles of bar magnet can never be separated to each other.

23. A person rings, a metallic bell near a strong concrete wall. He hears the echo after 0.3 s. If the sound moves with a speed of 340 m/s, how far is the wall from him? [Morning Shift-2016 (I)]

Correct Answer: (c) 51 m
Solution:

The sound that is heard after the first ring is due to reflection of sound at the surface of wall is called echo. Total distance travelled by sound in going to the surface and back
= Speed × Time
So, the distance of the wall (surface) from the sound source
= 1/2 × Speed × Time
= 1/2 × 340 × 0 3. = 51m
Hence, option (c) is correct.

24. A body is falling freely under the action of gravity alone in vacuum. Which one of the following remains constant during the fall? [Morning Shift-2016 (I)]

Correct Answer: (d) Total mechanical energy
Solution:

During the free fall of a body under the action of gravity of earth, total mechanical energy always remains constant.
Total mechanical energy = Kinetic energy + Potential energy
1/2 mv² + mgh = constant

25. X-rays are [Morning Shift-2016 (I)]

Correct Answer: (d) not deflected by an electric field and a magnetic field
Solution:

Since, X-ray is a high energy photons, which don’t carry any charge. So, it is not deflected by an electric field and a magnetic field.

26. The focal length of the lens of a normal human eye is about [Morning Shift-2016 (I)]

Correct Answer: (d) 2.5 cm
Solution:

The focal length or the distance from the corner of the retina of a normal relaxed eye is about 1.7 cm and 2.3 cm. So, the nearest value of the given option is 2.5 cm.

27. Which one of the following physical quantities is the same for molecules of all gases at a given temperature? [Morning Shift-2016 (I)]

Correct Answer: (c) Kinetic energy
Solution:

According to kinetic theory of gases, for molecules of all gases at a given temperature have the same average kinetic energy.

28. Newton’s laws of motion do not hold good for objects [Morning Shift-2016 (I)]

Correct Answer: (d) moving with velocity comparable to velocity of light
Solution:

Newton’s laws of motion do not hold good for objects moving with velocity comparable to velocity of light as there is a change in mass of body.

29. Which one of the following statements is not correct? [Morning Shift-2016 (I)]

Correct Answer: (d) Weight and mass of a body are equal at sea level on the surface of the earth.
Solution:

Weight and mass of a body are not equal at sea level on the surface of the earth, because mass is the total content of the body and weight is the force of attraction by which centre of earth attract any mass.

30. A brick is thrown vertically from an aircraft flying 2 km above the earth. The brick will fall with a [Morning Shift-2016 (I)]

Correct Answer: (c) constant acceleration
Solution:

During free fall of a body, the physical quantity which remains constant is acceleration due to gravity g of the earth, which remains constant in magnitude and directed towards the centre of earth.