Physics MCQs

Notes:
The speed of sound in a medium is determined by the properties of that medium, primarily its density and elasticity. The speed of sound is fastest in solids, followed by liquids, and then gases. Let’s analyze the given options:

[A] Air at zero degrees Celsius: The speed of sound in air increases with temperature. At lower temperatures, the molecules in the air have less kinetic energy, which results in a slower speed of sound. So, the speed of sound in air at 0°C is slower compared to higher temperatures.

[B] Air at 100 degrees Celsius: As mentioned earlier, the speed of sound in air increases with temperature. So, the speed of sound in air at 100°C would be faster than at 0°C but still slower than in a solid or liquid.

[C] Water: The speed of sound in water is significantly faster than in air. Water is denser and more elastic than air, which allows sound waves to travel through it more quickly.

[D] same in all: This statement is not correct. The speed of sound varies depending on the medium. It is not constant and is definitely not maximum everywhere.

So, among the given options, the maximum speed of sound would be in “Water” (Option C).

Notes:
When two drops of mercury come into contact, they will tend to merge together and form a single drop with a minimum surface area. This is because of the properties of mercury, which is a liquid metal with a high surface tension. The surface tension of a liquid is a measure of its elasticity, and it is determined by the cohesive forces between the molecules of the liquid. In the case of mercury, the high surface tension causes the molecules at the surface of the liquid to be strongly attracted to each other, which results in the formation of a relatively smooth and spherical surface. When two drops of mercury are brought together, the surface tension causes them to merge and form a single drop with the smallest possible surface area. This phenomenon is known as the “minimization of surface area” and it is a common feature of liquids with high surface tension.

Notes:
Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. The capillary action is among the following works while we wipe with a towel.

Notes:
The speed of sound in a medium depends on temperature of the medium. The speed of sound decreases when we go from solid to gaseous state. In any medium as we increase the temperature the speed of sound increases.. The speed of sound will be highest in humid air at 30°C.

Notes:
To calculate the distance of the object from the source of sound based on the time taken for the echo, we can use the formula for distance traveled by sound:

Distance = (Speed of Sound × Time) / 2

The speed of sound in air at normal room temperature (20°C) is approximately 343 meters per second (m/s).

Given that the time taken in the echo is 5 seconds, we can plug the values into the formula:

Distance = (343 m/s × 5 s) / 2 Distance = 1715 meters / 2 Distance ≈ 857.5 meters

So, the approximate distance of the object from the source of sound is approximately 857.5 meters.

Notes:
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:
J.J Thompson was the first scientist to discover and identify the electrons and to make the discovery of the first subatomic particle. He was also the first scientist to find evidence for isotopes of a stable (non-radioactive) element in 1913, as part of his exploration into the composition of canal rays (positive ions). His experiments to determine the nature of positively charged particles led to the development of the mass spectrograph. J.J Thompson belonged to United Kingdom. He won the Nobel Prize in Physics in 1906 for his work on the conduction of electricity in gases.

Notes:
Non-uniform motion refers to the motion where the objects cover equal distances in unequal time or unequal distances in equal time. In other words, when the speed of the object is not constant, or the direction of movement of an object changes, then it is in non-uniform motion. An example of this can be any vehicle moving on a crowded city road, where it constantly changes its speed.

Notes:
The slope of a straight line joining two points on a velocity-time graph gives the average acceleration between these two points. Depending on the sign of slope, the average acceleration can be positive or negative.

Notes:
The thrust on the rocket is in the opposite direction of the rocket. The thrust is the force with which rocket moves upwards. F = -u (dm/dt)