Questions Related to physics

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

A false balance is such that the beam remains horizontal when the pans are empty. An object weighs ${ w } _{ 1 }$ when placed in one pan and ${ w } _{ 2 }$ when placed in the other pan. Then the weight W of the object is

  1. $\sqrt { { w } _{ 1 }{ w } _{ 2 } } $

  2. $\dfrac { { w } _{ 1 }+{ w } _{ 2 } }{ 2 } $

  3. $\dfrac { 2 }{ \sqrt { { w } _{ 1 }^{ 2 }+{ w } _{ 2 }^{ 2 } } } $

  4. $\sqrt { \dfrac { { w } _{ 1 }^{ 2 }+{ w } _{ 2 }^{ 2 } }{ 2 } } $

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For a false balance with equal arm lengths but unequal pan weights or other systematic errors, the true weight is the arithmetic mean of the weights obtained in the two pans: W = (w1 + w2) / 2.

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

An object hangs from a spring balance. The balance indicates  $30 { N }$  in air and  $20 { N }$  when the object is submerged-in.water. What does the balance indicate when the object is submerged in a liquid. with a density that is half that of water ?

  1. $20 N$

  2. $25 N$

  3. $30 N$

  4. $35 N$

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The buoyant force is proportional to the density of the liquid. In water, the loss is 30 - 20 = 10 N. In a liquid with half the density of water, the buoyant force is half, which is 5 N. The reading is 30 - 5 = 25 N.

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

A man is standing on a weighting machine with a block in his hand. The machine records $W$. When he takes the block upwards with some acceleration the machine records $W _1$. When he takes the block down with some acceleration, the machine records $W _2$. Then choose correct option 

  1. $W _1 = W = W _2$

  2. $W _1 < W < W _2$

  3. $W _2 < W < W _1$

  4. $W _2 = W _1 > W$

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When the block is accelerated upward, the man exerts more force on the machine (W1 > W). When accelerated downward, the man exerts less force on the machine (W2 < W). Thus, W2 < W < W1.

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

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

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Coriolis force affects the apparent weight of an object on a moving ship. The change in weight depends on the direction of travel relative to the Earth's rotation, leading to the +/- term.

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

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

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This involves a pulley system in an accelerating elevator. The effective acceleration is g + a. The tension in the string for a pulley system with masses m1 and m2 is T = 2 * m1 * m2 * (g+a) / (m1 + m2).

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

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

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The apparent weight is W = m(g - a). Here, W = 50 * (10 - 9) = 50 * 1 = 50 N. In terms of mass reading, this is 5 kg.

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

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. $W _2 &lt; W _1$, due to the force of buoyancy acting on the filled balloon

  3. $W _2 &gt; W _1$ 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

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When the balloon is filled with air at higher pressure, the density of the air inside is greater than the density of the air outside, making the filled balloon heavier.