Free Physics in Daily Life MCQs with Answers

31. An iceberg is floating in sea. How much of its mass will remain above the surface of water?

• A. One tenth
• B. One fifth
• C. One fourth
• D. One third

Explanation: An iceberg floats with roughly one-tenth of its volume, and approximately one-tenth of its mass, above seawater because ice is less dense than seawater. The remaining nine-tenths is submerged.

32. The sun appears red at sunrise and sunset while it appears white at noon, because

• A. Of refraction
• B. It is cooler at sunrise and at sunset
• C. Of diffraction leading to red end of the spectrum reaching the earth.
• D. Of Scattering of light due to dust particles and air molecules.

Explanation: At sunrise and sunset, sunlight travels through a longer path in the atmosphere, so shorter blue wavelengths are scattered more and red light reaches the eye. At noon, the shorter atmospheric path makes the Sun appear nearly white.

33. An astronaut inside a spacecraft is in a state of weightlessness. This implies that?

• A. The mass of the astronaut is reduced to zero
• B. Gravity inside the spacecraft ceases to act
• C. The astronaut is outside the influence of the earth's gravitational force
• D. The astronaut and the spacecraft are both in a free-failing state

Explanation: Weightlessness means the astronaut and spacecraft are falling together under gravity, so no supporting force is felt. Earth’s gravity still acts, and the astronaut’s mass does not become zero.

34. A lake starts freezing because of the cold atmosphere. It will first freeze

• A. At the bottom
• B. ln the middle pan
• C. At the top surface
• D. Uniformly throughout the water body

Explanation: Water cools from the surface, and the colder, denser water sinks until it reaches about 4°C. Further cooling makes surface water less dense, so ice forms first at the top and then insulates the water below.

35. Cobalt is a material which is ?

• A. Strongly attracted by a magnet
• B. Not attracted by a magnet
• C. not a magnet
• D. Weakly attracted by a magnet
• E. None of these

Explanation: Cobalt is ferromagnetic, so it is strongly attracted to a magnet and can be magnetised. Iron and nickel show the same important magnetic property.

36. A body can escape the gravitational pull of the earth if it is thrown up with a velocity of?

• A. 25 miles per sec
• B. 60 miles per sec
• C. 7 miles per sec
• D. 10 miles per sec
• E. None of these

Explanation: Earth's escape velocity is about 11.2 km/s, or approximately 7 miles per second, ignoring air resistance. At this speed, an object can escape Earth's gravitational field without further propulsion.

37. Magnifying power of a simple microscope can be increased by ?

• A. increasing focal length of the lens
• B. Decreasing focal length of the lens
• C. Lens of large aperture
• D. lens of short aperture
• E. None of these

Explanation: For a simple microscope, magnifying power increases as the focal length decreases, since its angular magnification is approximately proportional to 1/f. Aperture mainly affects brightness and resolving ability, not the basic magnification here.

38. Cusec is a unit of _________?

• A. Area
• B. Time
• C. Distance
• D. mass
• E. None of these

Explanation: A cusec means one cubic foot per second, so it measures the rate of flow of a fluid. None of the listed choices names a flow-rate unit.

39. The principle used in radar is the same as that of Sonar. In radar we use radio waves ; whereas in sonar we use ?

• A. red waves
• B. Infrared waves
• C. Ultrasonic
• D. super sonic
• E. None of these

Explanation: Sonar uses ultrasonic sound waves, whose frequencies are above the human hearing range. Radar uses electromagnetic radio waves, so the two systems use different kinds of waves despite similar echo-based principles.

40. A six feet tall lady wants to see her full image in a plane mirror . The minimum length of the mirror will be ?

• A. 6 feet
• B. 12 feet
• C. 4 feet
• D. 3 feet
• E. None of these

Explanation: A plane mirror only needs to be half as tall as the observer for the observer to see the complete body, because rays from the head and feet reach the mirror at halfway points. For a six-foot person, the minimum mirror length is therefore three feet.