## Wednesday, April 24, 2019 # WBCS Questions and Answers on General Science (Physics) P8

71. If the density of air is 1.30 g/lit., what is the volume occupied by 7.8 g of air?
(A) 6.5 lit.
(B) 10.10 lit.
(C) 10 lit.
(D) 6 lit

72. Which of the following metals is the best conductor of heat and electricity
(A) Silver
(B) Potassium
(C) Sodium
(D) Copper

73. The kinetic energy of molecules is highest in
(A) Liquids
(B) Solutions
(C) Gases
(D) Solids

74. When loaded and empty trucks of identical specifications, are moving with the same velocity, more force is required to stop the loaded truck. Which of the following Laws is proved by this action?
(A) Newton's third law of motion
(B) Gravitational law
(C) Newton's first law of motion
(D) Newton's second law of motion
Correct Answer: [D] Newton's second law of motion.

75. Which one of the following is the weakest force?
(A) Gravitational force
(B) Electrostatic force
(C) Nuclear force
(D) Electromagnetic force

76. If the length and cross-section of a Wire are both doubled, the resistance will
(A) Increase twice
(B) Remain unchanged
(C) Increase 4 times
(D) Decrease 5 times

77. A solid piece of iron sinks in water but floats in mercury because -
(A) the density of iron is more than that of water as well as mercury
(B) the density of iron is more than that of water but less than that mercury
(C) the average density of water & mercury is less than that of iron
(D) the density of iron is less than that of water as well as mercury
Correct Answer: [B] the density of iron is more than that of water but less than that mercury.

78. When the water cools from 7°C to 0°C
(A) It first contracts and then expands
(B) It first expands and then contracts
(C) It contracts only
(D) It expands only
Correct Answer: [A] It first contracts and then expands.

79. When a positively charged conductor is earthed, then
(A) Electrons flow from the earth to the conductor
(B) Protons flow from the earth to the conductor
(C) Electrons flow from the conductor to the earth
(D) Protons flow from the conductor to the earth
Correct Answer: [A] Electrons flow from the earth to the conductor.

80. If the temperature is kept constant during a reaction, the process is called
(A) Isochoric
(B) Isothermal