Physics MCQs

Notes:
When a barometer is taken down into a coal mine, the mercury level rises. This is because the temperature increases as you move down the Earth’s crust. There is also very little wind, so the warmth can’t distribute the temperature and moderate it.  A barometer is an instrument that measures pressure. In a coal mine, the pressure is higher than normal pressure. When a barometer is taken down into a coal mine, it shows a greater reading.

Notes:
The correct answer is “electrostatic force of attraction.” In an atom, electrons are negatively charged and are attracted to the positively charged nucleus due to Coulomb’s law. This attraction provides the necessary centripetal force to keep the electron in a stable orbit around the nucleus. The balance between this electrostatic force and the electron’s inertia allows for stable atomic structures.

Notes:
The weight of a person becomes zero in a lift. Lift moves down with an acceleration of 9.8 meter per sq. second.

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A Balloon filled with a gas such as Hydrogen gas is much lighter in weight than the weight of air displaced by it. So the buoyant force exerted by the air on a balloon is greater than the weight of the balloon. The hydrogen gas which is lighter than air enables the balloon to float.

Notes:
X-rays were discovered by Wilhelm Conrad Roentgen. W.C Roengten discovered X-Rays while actually working on Cathode rays. X-rays is a form of electromagnetic radiation having a wavelength ranging from 0.01 to 10 nanometers and frequencies in the range 30 petahertz to 30 exahertz. Some Uses of X-Rays: The main use of X-rays is in medicine to check for a broken bone inside body. X-rays can also be used to kill cancer cells. X-rays are used at security checks at airports, railway stations etc. to check customers and baggage. X-rays are also used art historians to see if a picture has been painted on top of an older one. X-ray diffraction is also very important in spectroscopy and as a basis for X-ray crystallography.

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Electromagnetic force is the force between charged particles. It can be attractive for unlike charges and repulsive for like charges. It does not need any intervening medium to act and is enormously strong as compared to gravitational force.

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One dyne force is that much force which produces an acceleration of 1 cm s^-2 in a body of mass one gram. 1 dyne = 1 g cm s^-2 Also, 1 N = 10⁵ dyne

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Potential energy is stored in the spring of a watch. Potential energy is the energy by virtue of an object’s position relative to other objects. It is often associated with restoring forces such as a spring or the force of gravity.

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The minimum speed required to put a satellite into a given orbit around earth is known as Orbital velocity of the satellite. Orbital velocity (v) = (GM/r)^1/2 where G= gravitational constant, M= mass of the earth and r = radius of the orbit of the satellite.

Notes:
A common unit of pressure is the atmosphere (atm), i.e. the pressure exerted by the atmosphere at sea level (1 atm = 1.013 × 10⁵Pa).