Physics MCQs

Notes:
The mean value of the acceleration due to gravity (often denoted as “g”) at Earth’s surface is approximately 9.81 meters per second squared (m/s²). This value represents the average gravitational acceleration experienced by objects on the surface of the Earth. It is important to note that this value is not constant everywhere on Earth’s surface and can vary slightly due to factors such as location, altitude, and the density of the Earth’s crust.

Notes:
The ohm is the SI unit of electrical resistance. Electrical resistance of an object is the measure of its obstruction to the flow of electric current. It mainly depends on the material it is made of, cross sectional area of a conductor, length and temperature. The resistance of a conductor of unit cross-sectional area and unit length is known as Resistivity. The unit of resistivity is ohm-metre.

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Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 gigahertz to as low as 30 hertz. It is used to measure the speed of an approaching car.

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Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. Surface tension allows insects, usually denser than water, to float and slide on a water surface. It is the reason for the water droplet’s round shape.

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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.

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one watt is the rate at which work is done when an object is moved at a speed of one meter per second against a force of one Newton.

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Low Earth Orbit (LEO) is more prone to space debris or space junk. This is because space debris is more concentrated in orbits closer to Earth. Most debris is within 2,000 km (1,200 miles) of Earth’s surface.
Space debris orbits the Earth at tremendous speeds, about 15,700 miles per hour (25,265 kph) in low Earth orbit. In the event of a collision, it could cause significant damage to a satellite or spacecraft.
Experts are concerned about the amount of space debris in regions that are too high to benefit from the cleansing effects of Earth’s atmosphere. They believe that if there is too much space junk in orbit, it could result in a chain reaction where more and more objects collide and create new space junk.

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At the lowest point of its motion of swinging pendulum, kinetic energy is maximum and gravitational potential energy is minimum. At the highest point of its motion, kinetic energy is minimum and gravitational potential energy is maximum.

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The reason is the anomalous expansion of water. The maximum density of water occurs at 4°C. So the water expands whether it is heated above 4°C or cooled below 4°C.

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When the elevator is slowing down while moving downwards, that means there is an acceleration upwards. The gravitational force must be lesser than the normal force. Thus, during slowing down while moving downwards, the normal force on the feet of a passenger is greater than her weight. In this case the scale will read more than 80 kg.