# 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:

1. 20 N

2. 20 $\sqrt{3}$ N

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

4. zero

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?

1. Force

2. Energy

3. Power

4. Stress

Correct Option: D

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

1. True

2. False

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 :

1. 1 newton

2. 1 Newton

3. 1 NEWTON

4. None of these

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

1. $1GW$

2. $1MW$

3. $1TW$

4. none of these

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?

1. 1 Watt

2. 1 W

3. 1 w

4. 1 wt

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

1. Lower initial letter

2. Initial capital letter

3. Lower letter

4. All

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 :

1. $m$

2. $M$

3. $\mu$

4. All of the above

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

1. Lower initial letter

2. Initial capital letter

3. Lower letter

4. All

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 :

1. $10^2$

2. $10$

3. $10^{-1}$

4. $10^{-2}$

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  $\dfrac{m/s^2}{cm/s^2} = \dfrac{100 \ cm/s^2}{cm/s^2} = 10^2$