Tag: motion and measurement

Questions Related to motion and measurement

An atmosphere:

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. Is a unit of pressure

  2. Is a unit of force

  3. Gives an idea of the composition of air

  4. Is the height above which there is no atmosphere

Show answer
Correct Option: A
Explanation:

An atmosphere is defined as the unit of pressure because we use to write the atmospheric pressure in terms of the $atm$.


So, it is a unit of pressure. Option $A$ is correct.

In a screw gauge, 5 complete motations of the screw cause it to a linear distance of 0.25 cm. There are 100 circular scale divisions. The thickness of a wire measured by this screw gauge gives a reading of 4 main scale divisiors and 30 circular scale divisions. Assuming negligible zero, the thickness of the wire is:

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. $0.4300$ cm

  2. $0.2150$ cm

  3. $0.3150$ cm

  4. $0.0430$ cm

Show answer
Correct Option: B
Explanation:
In one rotation, scale moves $\dfrac{0.25}{5}=0.05\,cm$

Least count $=0.05\times 10^{-2}\,cm$

For $4$main scale division $=4\times 0.05=0.2\,cm$

For circular scale division $30\times 0.05\times 10^{-2}=1.5\times 10^{-2}\,cm$

Thickness of wire $0.2+0.015=0.2150\,cm$

Assuming the length of the day uniformly increases by $0.001$ second per century. The net effect on the measure of time over $20$ centuries is?

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. $3.2$ hour

  2. $2.1$ hour

  3. $2.4$ hour

  4. $5$ hour

Show answer
Correct Option: B

In particular system of unit, if the unit of mass becomes twice and that of time becomes half, then $8$ Joules will be written as _______ units of work

physics dynamics - explaining motion physical quantities motion and measurement units - definitions and systems

  1. $16$

  2. $1$

  3. $4$

  4. $64$

Show answer
Correct Option: D
Explanation:
The unit of work is $kg\ m^2/s^2$.

$8Joule=\dfrac { 8M{ L }^{ 2 } }{ { T }^{ 2 } }$

$ =\dfrac { 8(1kg){ (1m) }^{ 2 } }{ { (1s) }^{ 2 } } $

On doubling the unit of mass and unit of time is halved:
$=\cfrac { 8(2\quad unit\quad of\quad mass){ (1m) }^{ 2 } }{ { \left( \frac { 1 }{ 2 } unit\quad of\quad time \right)  }^{ 2 } }$

$ =\dfrac { 8\times 2 }{ { \left( \frac { 1 }{ 2 }  \right)  }^{ 2 } } units\quad of\quad work\\ =64\ units\quad of\quad work.$