Tag: measurements and units

Questions Related to measurements and units

A body is suspended on a spring balance in ship sailing along the equator with a speed $V$. If $\omega$ is the angular speed of the earth and ${W} _{0}$ is the scale reading when the ship is at rest, the scale reading when the ship is sailing will be very close to:

  1. ${W} _{0}$

  2. ${W} _{0}(1+\cfrac{2\omega V}{g})$

  3. ${W} _{0}(1\pm\cfrac{2\omega V}{g})$

  4. none of these


Correct Option: C

Find the reading of the spring  balance, when the elevator  is going  up with an acceleration of g /10 the pulley is smooth 

  1. 3.1 kg

  2. 4.4 kg

  3. 1.8 kg

  4. 6.2 kg


Correct Option: A

A person of mass 50 kg stands on a weighing scale on a lift. If the lift is descending with a downwards acceleration of $9 ms^{-2}$, what would be the reading of the weighing scale ? $(g = 10 ms^-2)$

  1. 5 kg

  2. 10 kg

  3. 15 kg

  4. 20 kg


Correct Option: A

A wooden block reads 0 kg wt on a spring balanced,when the block is immersed in water the reading of spring balance will be.
$ [p _{wood} = 0.8 gm/cm^3] $ 

  1. 8 kg wt

  2. 2 kg wt

  3. 6 kg wt

  4. zero


Correct Option: D

If a spring balance having frequency $f$ is taken on moon (having $ gravity = g/6$) it will have a frequency of

  1. $6f$

  2. $\dfrac{f}{3}$

  3. ${f}$

  4. $3f$


Correct Option: C

What is the net force on a bathroom scale when a 100 kg person stands on it ? $(g = 10 ms^-2)$

  1. 100 N

  2. 1000 N

  3. 50 N

  4. 0 N


Correct Option: D

The weight of a balloon is $W _1$ when empty and $W _2$ when filled with air. Both are weighed in air by the same sensitive spring balance and under identical condition. Then

  1. $W _1=W _2$, as the weight of air in the balloon is offset by the force of buoyancy on it

  2. $W _2 < W _1$, due to the force of buoyancy acting on the filled balloon

  3. $W _2 > W _1$ as the air inside is of a greater pressure and hence has greater density than the air outside

  4. $W _2=W _1+$ weight of the air inside it


Correct Option: C

Which of the following is not true of the standard weights and Measures? 

  1. Larger weights are made of iron

  2. Smaller weights are made of lead

  3. The value is written on the top

  4. They are either hexagonal or circular in shape


Correct Option: C

What principle is used In a  newton spring balance?

  1. The mass of an object depends on its density.

  2. The mass of an object depends an the gravity pulling

  3. The weight of an object is directly proportional to its mass.

  4. The extension of the spring is directly proportional to the force pulling it.


Correct Option: D

Which of the following principle helps in the measurement of mass of the planets?

  1. Einstein's theory of relativity

  2. Newton's Law of gravitation

  3. Newton's Law of cooling

  4. Parallax Method


Correct Option: B
Explanation:

With the help of Newton's law of gravitation we can measure mass of planets.

Newton's law of universal gravitation states that a particle attracts every other particle in the universe using a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

$F=\dfrac { G{ m } _{ 1 }{ m } _{ 2 } }{ { r }^{ 2 } } $   where $m _1$ amd $m _2$ are mass of planets, and $r$ is the distance between them  and $G$ is gravitation constant.
From this we can measure mass of planets.