Tag: physics

Questions Related to physics

A body of  weight 20 N is on a horizontal surface, minimum force applied to pull it when applied force makes an angle $60^0$ with horizontal (angle of friction a = $30^0$) is:

friction laws of motion physics

  1. 20 N

  2. 20 $\sqrt{3}$ N

  3. $\dfrac{20}{\sqrt{3}}$ N

  4. zero

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Correct Option: C
Explanation:
For minimum force, we will use limiting friction  i.e.
$\Rightarrow \tan\phi=\mu _{s}$
and ATQ, $\phi=30$
$\Rightarrow \tan 30=\mu _{s}$
$\Rightarrow \mu _{s}=\cfrac{1}{\sqrt 3}$
Minimum force can be calculated as $=\mu _{s}mg$
ATQ, $mg=20N, \mu=\cfrac{1}{\sqrt 3}$
$\Rightarrow F _{min}=\cfrac{20}{\sqrt 3}N$

If units of mass and length are doubled and that of time remains same, in which quantity numberical value is unchanged?

physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

  1. Force

  2. Energy

  3. Power

  4. Stress

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Correct Option: D

When a symbol is used to represent a unit named after a person,  lower-case letters are used.

physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

  1. True

  2. False

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Correct Option: B
Explanation:
The given statement is false because upper-case letters are used to represent the symbol of a unit named after a person.
For example : Newton is denoted by  $N$

The correct way to represent an unit amount of force is :

physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

  1. 1 newton

  2. 1 Newton

  3. 1 NEWTON

  4. None of these

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Correct Option: A
Explanation:

The full name of the unit, irrespective of the fact whether it is named after a scientist or not, is always written with the lower initial letter. Hence 1 newton is correct way to write.

The correct way to represent ${10}^{9}W$ is

physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

  1. $1GW$

  2. $1MW$

  3. $1TW$

  4. none of these

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Correct Option: A
Explanation:

A unit may not be written with double prefixes. So, ${10}^{9}W$ may be written as $1GW$ and not as $1kMW$ and $1mTW$.

Which of the following is the right way of expressing 1 watt of power?

physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

  1. 1 Watt

  2. 1 W

  3. 1 w

  4. 1 wt

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Correct Option: B
Explanation:

The symbol for a unit, which is named after a scientist, is written with the first letter of the name as capital. So, 1 watt will be expressed as 1 W.

The symbol for a unit which is not named in the honour of some scientist is written in

physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

  1. Lower initial letter

  2. Initial capital letter

  3. Lower letter

  4. All

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Correct Option: C
Explanation:

The symbol for a unit which is not named in the honor of some scientist is written in lower letter.ex:- the symbol for metre is 'm',for kilo gram is 'kg' and for second is 's'.

The symbol for metre is written as :

physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

  1. $m$

  2. $M$

  3. $\mu$

  4. All of the above 

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Correct Option: A
Explanation:

The symbol for metre is 'm' ,for kilogram is 'kg' and for second is 's'.

Full name of the unit named in the honour of a scientist is written with

physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

  1. Lower initial letter

  2. Initial capital letter

  3. Lower letter

  4. All

Show answer
Correct Option: A
Explanation:

Full name of the unit named in the honour of a scientist is written with lower initial letter. For example, the full form for unit of force is newton and not Newton.

The ratio of SI unit to CGS unit of $g$ is :

physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

  1. $10^2$

  2. $10$

  3. $10^{-1}$

  4. $10^{-2}$

Show answer
Correct Option: A
Explanation:

SI unit of $g$ is   $m/s^2$
CGS unit of $g$ is  $cm/s^2$
We know that  $1 \ m = 100 cm$
Thus ratio of SI unit to CGS unit  $\dfrac{m/s^2}{cm/s^2} = \dfrac{100 \ cm/s^2}{cm/s^2} = 10^2$