Free Physics in Daily Life MCQs with Answers

71. BTU is a unit of________?

• A. Force
• B. Magnetic flux
• C. Energy
• D. None of these

Explanation: A British thermal unit, or BTU, is a unit of heat energy, historically defined as the heat needed to raise one pound of water by one degree Fahrenheit. It is not a unit of force or magnetic flux.

72. In an atomic nucleus, neutrons and protons are held together by: ___________?

• A. Gravitational forces
• B. Exchange forces
• C. Coulombic forces
• D. Magnetic forces

Explanation: Protons and neutrons are bound inside the nucleus by the strong nuclear interaction, often described in older texts as an exchange force involving exchange particles. Gravity is far too weak at nuclear distances, while electric repulsion acts between protons.

73. According to Quark theory, there are _________ elementary particles.

• A. Three
• B. Six
• C. Nine
• D. Ten

Explanation: The quark model recognises six quark flavours: up, down, charm, strange, top and bottom. They combine to form composite particles such as protons and neutrons.

74. Which of the following phenomena of light are involved in the formation of a rainbow?

• A. Refraction
• B. Dispersion
• C. Total internal reflection
• D. All of the above

Explanation: Rainbows form when sunlight is refracted and dispersed into colours inside raindrops, then undergoes internal reflection before being refracted again as it exits. Thus all three listed optical effects are involved.

75. What colour is called magenta?

• A. Black
• B. White
• C. Yellow
• D. Reddish-Purple

Explanation: Magenta is a purplish-red colour produced by combining red and blue light or pigments. It is not one of the basic black, white, or yellow choices listed.

76. A Cheetah can accelerate to 100 kmph in just__________.

• A. 3 seconds
• B. 6 seconds
• C. 9 seconds
• D. 12 seconds

Explanation: A cheetah can reach about 100 km/h from rest in roughly three seconds, making its acceleration exceptional among land animals. The longer times listed are less consistent with its famous short sprint acceleration.

77. Natural Radioactivity was discovered by Becquerel in ____________?

• A. 1766
• B. 1896
• C. 1935
• D. 2001

Explanation: Henri Becquerel discovered natural radioactivity in 1896 while studying uranium salts. His observation preceded the later work of Marie and Pierre Curie.

78. Rainbow is seen after rain because of hanging molecules of water which act as __________?

• A. Lens
• B. Prism
• C. Mirror
• D. Slabs

Explanation: Raindrops disperse sunlight by refraction, internal reflection, and refraction again, acting approximately like tiny prisms. This separates white sunlight into the colours of a rainbow.

79. The frequency of ultrasound wave is typically?

• A. Above 20 kHz
• B. Above 20,000 kHz
• C. Below 20 kHz
• D. Below 02 kHz

Explanation: Ultrasound consists of sound waves above the upper human hearing limit of about 20 kHz. Frequencies below 20 kHz are generally within the audible range for humans.

80. Kinetics is the study of________.

• A. Motion and its causes
• B. Force and energy
• C. Friction
• D. Heat and temperature

Explanation: Kinetics studies motion together with the forces and torques that cause or change it. Kinematics describes motion without considering its causes, which is the common distinction.