Tag: physics

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Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

In a large commercial complex there are four ways to reach the main road. One of the path has loose soil, the second is laid with polished marble, the third is laid with bricks and the fourth has gravel surface. It is raining heavily and Paheli wishes to reach the main road. The path on which she is least likely to slip is:

  1. loose soil

  2. polished marble

  3. bricks

  4. gravel surface
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Loose soil will provide the maximum friction and hence less chances of slipping.

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

Which of the following is used to reduce friction :
1. Streamlines
2. Use of ball bearings
3. Lubrication

  1. 1 & 2 only

  2. 1 & 3 only

  3. 2 & 3 only

  4. 1, 2 & 3
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All the mentioned option are correct.

Streamlines reduces the friction in fluid.
Use of ball bearing reduces the friction in machines rotating parts.
Lubricants are used in machines  and moving parts to reduce friction.

Option D is correct.

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

Why are efforts made to reduce friction?

  1. Energy is lost in overcoming friction.

  2. Overcoming friction is a time consuming process.

  3. Both A and B

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A lot of the applied energy is lost in overcoming friction so as to put a body in motion.Hence efforts are made to reduce friction.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

A sound wave travels from west to east, in which direction do the particles of air move?

  1. west-east

  2. south-north

  3. up-down

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sound waves are longitudinal waves and the particles of the air move in direction of propagation sound. So if the wave will travel in west-east direction,the particles of the air also travels in west-east direction.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

Mark the incorrect statement

  1. Sound can be produced by beating an object irrespective of whether there are vibrations or not.

  2. The sound of a tabla normally has a lower pitch than the sound of a violin.

  3. A short flute will produce sound of lower pitch than a long flute.

  4. All
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

(i) False [Sound is produced from a vibrating object.]

(ii) True [The sound of a tabla normally has a lower pitch than the sound of a violin.]

(iii) True[A short flute will produce sound of lower pitch than a long flute.]

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

Why are the regions of compressions and rare fractions of sound waves formed?

  1. A sound wave undergoes diffraction behind obstacles.

  2. The reflected sound wave at a fixed end interferes with the incident wave.

  3. The longitudinal movement of air molecules produces pressure fluctuations.

  4. The speed of the sound wave changes as its travels through a medium.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Longitudinal waves are made up of compressions and rarefactions. Compression happens when molecules are forced, or pressed, together. Rarefaction is just the opposite, it occurs when molecules are given extra space and allowed to expand. So, the longitudinal movement of air molecules produces pressure fluctuations which results in compression and rarefaction.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

A source emits the sound of frequency $600\ Hz$ inside water. The frequency heard in air will be equal to (velocity of sound in watere$=1500\ m/s$, velocity of sound in air$=300\ m/s$)

  1. $3000\ Hz$

  2. $120\ Hz$

  3. $600\ Hz$

  4. $6000\ Hz$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Frequency heard in the air will also be $600\space Hz.$ Whenever, the wave travels from one medium to another medium, its speed and wavelength changes but frequency remains same.