(c) mercury has high density and low vapour pressure
     (d) mercury is available in pure form
Ans : (c)
72. A small weight is put on the pressure cooker. It increases the pressure of the steam because:
     (a) the weight is proportionate to the steam required
     (b) area of contact is small
     (c) the weight stops the steam from escaping
     (d) of Bernoulli"s principle
Ans : (b)
73. Every object at a temperature above absolute zero :
     (a) radiates energy
     (b) occupies less space than it would at absolute zero
     (c) is a good heat insulator
     (d) must receive heat by convection
Ans : (a)
74. The emission offs-partide :
     (a) increases the atomic number by one
     (b) decreases the atomic number by one
     (c) increases the mass number by one
     (d) decreases the mass number by one
Ans : (a)
75. When an electric bulb breaks, there is a mild bang due to:
     (a) the chemical reaction between the enclosed gases
     (b) the compressed gases rushing out suddenly
     (c) the air rushing in to fill the evacuated space
     (d) None of the above
Ans : (c)
76. Kinetic Energy depends:
     (a) on the mass of the moving body
     (b) the velocity or speed of the moving body
     (c) the pressure of the moving body
     (d) both mass and velocity of the moving body
Ans : (d)
77. A bomb is dropped at a point from a moving aeroplane. The pilot observes that:
     (a) the bomb traverses a curved path and falls some distance behind that point
     (b) the bomb traverses a curved path and falls some distance ahead
     (c) the bomb drops vertically downward
     (d) the bomb remains stationary in the air for some time
Ans : (b)
78. When two bodies, a heavy one and a light one are acted upon by the same force for the same time then:
     (a) the light body builds up a lower velocity than the heavy one and the momentum gained is different in both cases"
     (b) the light body builds up a higher velocity than the heavy one and the momentum gained is different in both cases
     (c) the light body builds up a higher velocity than the heavy one and the momentum gained is the same in both cases
     (d) None of the above is correct
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