Tag: physics

Questions Related to physics

Which of the following statements are true for wave motion ?

physics properties of waves longitudinal and transverse waves travelling waves types of waves

  1. Mechanical transverse waves can propagate through all mediums

  2. Longitudinal waves can propagate through solids only

  3. Mechanical transverse waves can propagate through solids only

  4. Longitudinal waves can propagate through vacuum

Show answer
Correct Option: C
Explanation:

$1.$ Mechanical transverse waves cannot propagate through all the medium. They can only propagate through solids not in gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave.

$2.$ Longitudinal wave can propagate through all type of medium.
$3.$ Mechanical transverse wave can propagate through solids only.
$4.$ Longitudinal wave cannot propagate through vaccum.
Hence, option $C$ is correct.

A man sets his watch by the noon whistle of a factory at a distance of $1.5 km.$ Then the number of seconds his watch slower than the clock of the factory (velocity of sound $= 332 m/s$) is 

physics properties of waves longitudinal and transverse waves travelling waves types of waves

  1. $4.52 sec$

  2. $5.35 sec$

  3. $2.18 sec$

  4. $3.76 sec$

Show answer
Correct Option: A
Explanation:

time taken for the whistle to reach the person is $\dfrac{d}{v}$
$=\dfrac{1.5\times 1000}{332}=4.52sec$
$\therefore$ delay of his clock is $4.52s$

When a wave is reflected from a ___________ medium, there is no change of phase.

physics properties of waves longitudinal and transverse waves travelling waves types of waves

  1. rarer

  2. denser

  3. both

  4. none of the above

Show answer
Correct Option: A
Explanation:

when reflection of wave takes place from the denser medium then  it undergoes a phase change of $\pi$ . Since, here in question the phase is not changing so the medium must be rarer.

answer is A.

If object A and object B has no transfer of heat, then they both are in

physics temperature and heat applications of heat conduction applications of insulation clothes - our necessity

  1. Catalytic

  2. Thermal equilibrium

  3. Expansion

  4. None

Show answer
Correct Option: B
Explanation:

$Object \ A \rightleftharpoons Object\ B$
Both are at same temperature or there is not temperature difference between them.

Good conductor of heat is

physics temperature and heat applications of heat conduction applications of insulation clothes - our necessity

  1. Hydrogen

  2. Oxygen

  3. Nitrogen

  4. None

Show answer
Correct Option: D
Explanation:

All of them are gases, which are not good conductors of heat.

Air is a _______ conductor of electricity.

physics temperature and heat applications of heat conduction applications of insulation clothes - our necessity

  1. Good

  2. Bad

  3. Both

  4. None

Show answer
Correct Option: B
Explanation:

All gases are poor conductor of heat. Air is a very poor conductor of heat.

Air is a good conductor of heat. True or false.

physics temperature and heat applications of heat conduction applications of insulation clothes - our necessity

  1. True

  2. False

Show answer
Correct Option: B
Explanation:
False
Air is bad conductor of heat. It is due to the air trapped between the cotton molecules which gives warmth on taking quilt in winter It is due to air molecules trapped between wool fabrics which provide warmth to body during winter season.

Wearing black clothes in summer is more preferable. True or false.

physics temperature and heat applications of heat conduction applications of insulation clothes - our necessity

  1. True

  2. False

Show answer
Correct Option: B
Explanation:
False
Wearing black clothes in summer is not preferable as during summer there is more heat present in the atmosphere and black clothes absorb more heat comparatively. So, black clothes are not preferable during summer.

State whether given statement is True or False
Two thin blankets are more warmer than one thick blanket

physics temperature and heat applications of heat conduction applications of insulation clothes - our necessity

  1. True

  2. False

Show answer
Correct Option: A
Explanation:
The blanket do not insulate; actually air insulates.
Air is trapped in the space between two thin blankets. Since air is insulator of heat, it prevents the escape of body heat. The air can't pass deeper and the layers will stop the air in two thin blankets where as there are no layers and air can pass deeper in one thick blanket. That's why two thin blankets are usually warmer than one thick blanket.

Good conductors of heat is

physics heat transfer applications of heat conduction applications of insulation clothes - our necessity

  1. Copper

  2. Water

  3. Wood

  4. Glass

Show answer
Correct Option: A
Explanation:

Substances become bad conductors of heat when they contain a large number of free electrons. This is because the electrons contained in atom of these elements are not closely bond to nucleus.