65.A device used to measure heights above sea level is known as
   (a) altimeter
   (b) anemometer
   (c) dilatometer
   (d) potentiometer
Ans: (a)
66.The instrument used to measure atmospheric pressure is
   (a) Pyrometer
   (b) Eudiometer
   (c) Barometer
   (d) Hydrometer
Ans: (c)
67.A hydraulic brake in an automobile uses
   (a) a fluid to transmit the braking force
   (b) the force applied by the driver
   (c) hydrogen gas and not any liquid
   (d) a vacuum brake
Ans: (a)
68.In a hydraulic pressure
   (a) force on each square centimetre of the small piston is less than the force
       on each square centimetre of the large piston
   (b) the distance the small piston moves is equal to the distance the large
       piston moves
   (c) applied pressure is equally transmitted throughout the liquid in all
   (d) force acting on small piston is equal to the force acting on large piston
Ans: (c)
69.Mercury is used in a barometer because
   (a) its density being very high 13.6 g/cm3 the height of mercury column is
       conveniently small
   (b) at the ordinary temperature its vapour pressure is small
   (c) it is opaque and does not wet glass
   (d) All the above
Ans: (d)