Physics MCQs

Notes:
Astigmatism is due to imperfect spherical nature of eye lens. The focal length of eye lens is in two orthogonal directions become different so they cannot see objects in two orthogonal directions simultaneously. This defect in direction can be removed by using cylindrical lens in a particular direction.

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When the simple pendulum is taken to the moon, value of gravitational constant g will decrease and thus, its time period will increase.

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The weight of a person would be maximum at the poles, due to the higher gravitational force acting upon them in these regions. This occurs because Earth is an oblate spheroid, flattened at its poles and bulging at the equator, resulting in a shorter distance from the Earth’s center at the poles and a consequent higher gravitational pull. At the equator, the force is slightly weaker due to a greater distance from the Earth’s center. Weights at the Tropics of Cancer and Capricorn lie in-between the poles and equator, but are closer to the equator’s value.

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Uniform speed means no acceleration. If there is no acceleration and the vehicle is moving with uniform speed; the stone will fall over you.

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The velocity of an object undergoing uniform circular motion is always changing (because the direction is always changing). Further, since the acceleration is centripetal, it must always point toward the center of the circle; so, as the object moves around the circle, the acceleration vector is also constantly changing direction. Notice that for an object in uniform circular motion, both the velocity and the acceleration are changing because the directions of these vectors are always changing, even though their magnitudes stay the same. In this question, only speed remains unchanged.

Notes:
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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The apparent weight of the person becomes less than the actual weight when the elevator is accelerating downwards. The apparent weight of the person becomes more than the actual weight when the elevator is accelerating upwards.

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Joule is the absolute unit of work in S.I 1 joule = 1 Nm

• 1 joule= 10⁷ ergs (erg is the unit of work in c.g.s)
• 1 erg = 1 dyne cm
• Also, Kilogram-metre (kg-m) is the gravitational unit of work on S.I 1 kg-m = 9.8 j

Notes:
Work done does not depend on the time for which the force was applied. Work done is only dependant on the force and displacement. Time is involved in the case of Power only

Notes:
Potential energy of a satellite: -L²/mr² Potential energy of a satellite: -L²/2mr² Therefore, Potential energy= – 2 (Kinetic energy)