Physics Questions

Sound is a mechanical vibration and needs a medium for propagation. The higher the density of the medium, the faster the sound travels. So, sound cannot travel through vacuum.

As the sound travels faster in solids than liquids and gases, sound travels faster in the glass than Air and water.

A barometer is a tool that measures air pressure

A rising barometer indicates increasing air pressure, a falling barometer indicates decreasing air pressure.

In space, there is a nearly complete vacuum, so the air pressure is zero.

Sea appears blue in colour due to the scattering of the rays when they hit water molecules

Kelvin is used to measure Temperature,

Candela is used to measure Intensity of flame,

Steredian is used to measure Solid Angle.

The weight of the man mg is acting on the floor. As the lift is moving up with an acceleration, say a, the man too in it is having this acceleration. The force producing this acceleration is ma. By Newton's third law, this force will have an equal reaction pressing the floor equal to ma. Therefore the total resultant reaction on the floor is mg+ma = m(g+a) which is mg, the weight of the man. So (a) is correct.

Megahertz is used to measure wave frequencies, as well as the speed of microprocessors. One MHz represents one million cycles per second. The speed of microprocessors, called the clock speed.