Physics MCQs

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When an object covers distance which is directly proportional to the square of the time, its acceleration is constant. This is seen in the cases of falling objects. This relation between time and distance was first observed by Galileo.

Notes:
Mass of the moon is 1/100 times and radius of moon is 1/4 times that of the earth .Therefore, the gravitational attraction on the moon is about one sixth of that on the earth. Hence, the weight of an object on the moon is 1/6th of the weight on the earth.

Notes:
The separation of oil and water is caused due to the difference in surface tension of the two liquids. The water molecules stick together tightly and does not mix with the oil because water molecules are attracted to each other more strongly, forming an invisible gskinh of surface tension around each drop as compared to oil drop.

Notes:
Elasticity is the capability of an object to return to its former shape once a load inducing strain is removed. Young Modulus or elastic modulus [tendency to be deformed elastically (i. e. , non-permanently) when a force is applied to it. Steel is more elastic than that of rubber because it requires far more deforming force than rubber.

Notes:
The key to why clouds float is that the density of the same volume of cloud material is less than the density of the same amount of dry air. Just as oil floats on water because it is less dense, clouds float on air because the moist air in clouds is comparatively less denser than dry air.

Notes:
A door belongs to the second class of levers because its pivot (hinge) is at the end, the load (weight of the door) is at the center, while the effort (opening the door) is applied at the other end. A class 2 lever has the resistance or load in the middle, the fulcrum at one end and the effort at the other.

Notes:
The phenomenon of raising outer edge of the curved road above the inner edge is to provide necessary centripetal force to the vehiclesto take a safer turn and the curved road is called Banking of Roads. If a car is on a level (unbanked) surface, the forces acting on the car are its weight, mg, pulling the car downward, and the normal force, N, due to the road, which pushes the car upward. Both of these forces act in the vertical direction and have no horizontal component. If there is no friction, there is no force that can supply the centripetal force required to make the car move in a circular path – there is no way that the car can turn.

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The volume or intensity of sound is measured in units called decibels (dB), generally on a scale from zero to 140. The higher the number in decibels, the louder the noise.

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Mercury thermometers are based on the principle that liquids expand when heated and contract when cooled. So, when the temperature increases, the mercury expands and rises up the tube and when the temperature decreases it contracts and does the opposite.

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If the angle of incidence of light ray in the denser medium is greater than the critical angle of the concerned media pair, the light is not at all reflected into the rarer medium but is totally reflected. This is known as ‘total internal reflection’. The two conditions for total internal reflection to take place include that ray of light must pass from denser into rare medium and second that angle of incidence must be greater than critical angle.