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Multiple choice physics measurements and units measuring mass measurement of mass measuring instruments

In the arrangement shown, the pulleys are fixed and ideal, the strings are light, $m _{1} > m _{2}$ and $S$ is a spring balance which is itself massless. The reading of $S$ (in units of mass) is

  1. $m _{1} - m _{2}$

  2. $\dfrac {1}{2}(m _{1} + m _{2})$

  3. $\dfrac {m _{1}m _{2}}{m _{1} + m _{2}}$

  4. $\dfrac {2m _{1}m _{2}}{m _{1} + m _{2}}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The acceleration of the system $= \left (\dfrac {m _{1} + m _{2}}{m _{1} + m _{2}}\right )g$ and hence the tension $T$ in the string is $\left (\dfrac {2m _{1}m _{2}}{m _{1} + m _{2}}\right )g$. The reading of the spring balance is $T$ (in units of force) and $\dfrac {T}{g}$ (in units of mass).

Multiple choice physics measurements and units measuring mass measurement of mass measuring instruments

Spring of spring balance must be _______ in nature.

  1. Elastic

  2. Non-elastic

  3. Rubber

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

Spring balance is used to measure the weight of the object. The working principle of spring balance is Hooke's law. Since Hooke's law is valid only for elastic objects, thus spring used in the spring balance must be elastic in nature.

Multiple choice physics measurements and units measuring mass measurement of mass measuring instruments

The working principle of spring balance is :

  1. Newton's laws of motion

  2. Hooke's law

  3. Ohm's law

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

Spring balance is used to measure the weight of the object. When a load is hung on the spring, it stretches and the spring's extension is proportional to the weight of the object. The working principle of the spring balance is Hooke's law  which is  $F = -kx$.

Multiple choice physics measurements and units measuring mass measurement of mass measuring instruments

State whether given statement is True or False.
Weight of same object differs at different distances from the equator. 

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
We know that acceleration due to gravity differs at different distances from the equator but the mass of the object remains constant.
Weight of the object   $W = mg$
Thus weight of the object differs at different distances from the equator.
Multiple choice physics measurements and units measuring mass measurement of mass measuring instruments

State whether given statement is True or False.
Weight remains constant at all places.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Weight of the object  $W = mg$
We know that acceleration due to gravity $g$ differs at different distances from the equator but mass of the object remains constant. Thus, weight of the object varies at different places.
Thus the given statement is false.