Physics MCQs

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Hydroelectric power is a source of renewable energy. The kinetic energy of water falling from dam is used for rotating the turbines to rotate the armateur in generator producing electricity.

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The waves produced on the surface of water in the pond is an example of transverse waves as particles of the medium do not move along with the wave. Only the disturbance (energy) is carried forward. Another example of such waves is the vibrations of a string energy.

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Any object moving in a circle (or along a circular path) experiences a centripetal force that pushes or pulls the object towards the center of the circle. In the case of a car moving along a curve, as it makes a turn, the force of friction acting upon the turned wheels of the car provides centripetal force required for circular motion. The net force on a car travelling around a curve is the centripetal force, F MV r c .. 2 , directed toward the center of the curve. To minimize the effect of this force, banking of curve is observed on curved paths.

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The pitch of a sound is determined by the frequency of vibration of the sound waves. So higher the frequency the higher is the pitch. Frequency is often measured in units called Hertz (Hz). If a sound source vibrates at 100 vibrations per second, it has a frequency of 100 Hertz.

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Friction between two surfaces can be reduced by polishing them. The interlocking and projections are minimized by this method. Friction can also be reduced by applying lubricants between the contact surfaces to fill the fine pores or depressions in the surfaces and make them smooth. Friction does not depend on the area of contact.

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When a ball is thrown vertically upwards then its velocity starts decreasing as there is gravity operating in the opposite direction of the motion. Thus, kinetic energy starts decreasing and at maximum height Kinetic energy becomes zero and whole of the K. E converts into P. E at the time of the maximum height.

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For a hyper-metropic eye ,the near points shift away from the eye i. e. farther away from the normal near point (25cm). In a hypermetropic eye, the light is not bent sufficiently so that it focuses at a point behind the retina. Here a person sees well for distance but near vision is difficult and causes strain. Hence, hypermetropic people are called long-sighted. To correct the hypermetropic eye, a plus lens (convex lens) is used to focus image on retina.

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A compound microscope is a microscope which uses multiple lenses to collect light from the sample and then a separate set of lenses to focus the light into the eye or camera. The objective lens provides the primary magnification which is compounded (multiplied) by the ocular lens (eyepiece).

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Gamma rays are the highest energy electromagnetic radiation and typically have energies greater than 100 keV, frequencies greater than 1019 Hz, and wavelengths less than 10 picometers. They are typically produced from the decay of atomic nuclei. The most powerful sources of gamma-rays are caused by astronomical events.

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There are two specific heats of gases- Specific Heat at Constant Pressure (Cp) and Specific Heat at Constant Volume (Cv). Heat supplied at constant pressure is used up in two ways: (a) for doing work in expansion and (b) for raising the temperature by 1o C, while at constant volume heat supplied is used only for rise of temperature. Therefore, Cp is always greater than Cv. They are related as: Cp – Cv = R/J. This relation is called Mayer’s Relation.