The efficiency of energy conversion on the energy flow through a hydroelectric power is?

An object weighs 30N in air and 21N in water. The weight of the object when completely immersed in a liquid of relative density 1.4 is

Which of the following instruments is most suitable for measuring the outside diameter of a narrow pipe in a few millimeters in diameter?

Electrical power is transmitted at a high voltage rather than a low voltage because the amount of energy loss is due to

If the focal length of a camera is 20cm, the distance from the film at which the lens must be set to produce a sharp image of 100cm away is