Physics MCQs

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The sunlight that reaches the earth has ultraviolet A and ultraviolet B (UVA and UVB) rays. These ultraviolet rays are the main causes of damage to the skin from the sun. UVA and UVB rays affect the skin’s sensitivity to sun exposure in different ways.

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In 1647 the French scientist Blaise Pascal (1623–1662) discovered that water exerts the same pressure in all directions. This statement is known as Pascal’s Principle.
Pascal’s law states that increase in pressure at a point in the enclosed liquid in equilibrium is transmitted equally in all directions in liquid and to the Walls of the container. The working of hydraulic lift, hydraulic press and hydraulic brakes are based on Pascal’s law.

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A vehicle moving on a circular path experiences centripetal force. Centripetal force that acts on a body moving in a circular path and is directed towards the centre around which the body is moving.

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X-ray crystallography helps to determine the atomic and molecular structure of a crystal. The crystalline structure performs the diffraction and it causes a beam of incident X-rays to diffract into many specific directions.

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A pressure cooker on a stove with its lid tightly closed and the whistle in position is an example of a closed-system thermodynamic process. In a closed-system thermodynamic process, the container (in this case, the pressure cooker) is sealed, and there is no exchange of matter with the surroundings. The pressure cooker is designed to be airtight, so no air or steam can escape while it’s cooking. This sealed environment allows for the buildup of pressure and temperature inside the cooker, which, in turn, speeds up the cooking process.

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Gravity plays a role in flame formation. Modifying the gravity causes different flame types. The common distribution of a flame under normal gravity conditions depends on convection, as soot tends to rise to the top of a general flame, as in a candle in normal gravity conditions, making it yellow. In micro gravity or zero gravity, such as an environment in outer space, convection no longer occurs, and the flame becomes spherical, with a tendency to become more blue and more efficient (although it may go out if not moved steadily, as the CO2 from combustion does not disperse as readily in micro gravity, and tends to smother the flame).

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Gravitational Forces are the weakest forces in nature. They obey inverse square law as they vary inversely as the square of the distance between the two bodies. They are central forces and conservative forces. They operate over very long distances having an infinite range.

Notes:
1 femto metre is equal to 10^-15 metre. Some other metric prefixes are:

• nano = 10^-9
• pico = 10^-12
• atto = 10^-18
• tera = 10¹²
• peta = 10^-15
• exa = 10^-18

Notes:
The conditions for equilibrium for an object: 1. There is no linear motion of the object i.e. the resultant force on the object is zero 2. There should not be any rotational motion of the object i.e. the torque on the object should be zero 3. The potential energy of the object should be minimum for stable equilibrium.

Notes:
Work done will be zero: 1. When displacement is zero 2. When force is zero 3. When angle between force and displacement vector is zero