Units and Dimensions

Q. 1 joule is equal to

1. ${10}^{5}erg$
2. ${10}^{6}erg$
3. ${10}^{7}erg$
4. ${10}^{9}erg$

Q.

What do you understand by the term unit ?

Q.

What are the three requirements for selecting a unit of a physical quantity?

Q.

Define density and relative density?

__

Q.

what is the order of magnitude of a physical quantity ?

Q. Find the dimensions for relative density

Q.

A unitless quantity:

1. never has a nonzero dimension

2. always has a nonzero dimension

3. may have a nonzero dimension

4. does not exist

Q. A: When we change the unit of measurement of a quantity, its numerical value changes.
R: Smaller the unit of measurement, smaller is its numerical value.

1. A and R are correct and R is correct not correct explanation A
2. A and R are correct and R is correct explanation of A
3. A is true and R is false
4. A is false and R is true

Q. Two stones are thrown vertically upwards simultaneously with their initial velocities $u_1$ and $u_2$ respectively. The heights reached by them would be in the ratio of

1. $u_2^2:u_2^2$
2. $u_2:u_1$
3. $u_1^2:u_2^2$
4. $u_1:u_2$

Q.

A packet of 400 g and volume 200 cm3 is put in a water tank. The relative density of packet is

1. 2

2. 4

3. 400

4. 200

Q.

The value of a unit changes with space and time.

1. False

2. True

Q.

Relative density has no dimension.

1. True

2. False

Q.

______ Electricity is produced due to the flow of Electrons.

Q. The S.I. units of mass, force and weight respectively are :-

1. kg, N, N
2. N, kg, N
3. N, N, kg
4. N, kg, kg

Q. Three blocks A, B and C placed on a smooth horizontal surface are being pushed with a force of 60 N as shown below. The contact force between block A and B is 30 N and that between block B and C is 10 N. The ratio of masses of blocks A, B and C is

चिकने क्षैतिज पृष्ठ पर रखे तीन गुटकों A, B व C को नीचे दर्शाए अनुसार 60 N के बल से धकेला जाता है। गुटके A व B के मध्य सम्पर्क बल 30 N है तथा गुटके B व C के मध्य सम्पर्क बल 10 N है। गुटकों A, B व C के द्रव्यमानों का अनुपात है

1. 3 : 2 : 1
2. 6 : 3 : 2
3. 1 : 2 : 3
4. 1 : 1 : 1

Q.

___ is the quantity of a constant magnitude used to measure the magnitudes of other quantities of the same nature.

Q.

An object of 400 g has volume of 200 cm³. The relative density of object is

1. 200

2. 2

3. 400

4. 4

Q. What are the fundamental units in SI system? Name them along with their symbols. $\left[7\text{marks}\right]$

Q. Name the two supplementary physical quantities introduced to the SI system. Write their SI units.

Q.

A unitless quantity

1. may have a nonzero dimension

2. does not exist

3. never has a nonzero dimension

4. always has a nonzero dimension

Q.

A unit is a ________quantity used as a standard for measuring physical quantities.

Q. Three blocks A, B and C having masses m, 3m and 4m respectively are placed on smooth horizontal surface. Force F is acting on block A as shown below, then

तीन गुटकों A, B व C के द्रव्यमान क्रमशः m, 3m व 4m हैं, इन्हें चिकने क्षैतिज पृष्ठ पर रखा गया है। गुटके A पर नीचे दर्शाए अनुसार बल F कार्यरत है, तब

1. Net force on A is zero
   
   A पर नेट बल शून्य है
2. Net force on B is $\frac{3F}{8}$
   
   B पर नेट बल $\frac{3F}{8}$ है
3. Force acting on B due to C is $\frac{F}{2}$
   
   C के कारण B पर कार्यरत बल $\frac{F}{2}$ है
4. Acceleration of A, B and C are equal
   
   A, B व C के त्वरण बराबर हैं

Q. If two quantities have the same unit then they must have the same dimension.

1. True
2. False

Q.

How many bytes are there in a kilobyte?

1. $512$

2. $1024$

3. $2048$

4. $4096$

Q.

Convert the following as directed:

$17kg$ $200gm$ into $gm$.

Q. Can I know how to define time

Q. Define 'relative density'.

Q. DB relative density and density

Q. The dimensional formula of modulus of rigidity is

1. $\left[M{L}^2{T}^{-2}\right]$
2. $\left[M{L}^{-1}{T}^{-3}\right]$
3. $\left[M{L}^{-1}{T}^{-2}\right]$
4. $\left[M{L}^{-2}{T}^{-2}\right]$

Q. The density of most substances decreases with increase in temperature.

1. False
2. True