UNITS AND MEASUREMENTS Quiz-14

UNITS AND MEASUREMENTS Quiz-14

Dear Readers,

As per analysis for previous years, it has been observed that students preparing for NEET find Physics out of all the sections to be complex to handle and the majority of them are not able to comprehend the reason behind it. This problem arises especially because these aspirants appearing for the examination are more inclined to have a keen interest in Biology due to their medical background. Furthermore, sections such as Physics are dominantly based on theories, laws, numerical in comparison to a section of Biology which is more of fact-based, life sciences, and includes substantial explanations. By using the table given below, you easily and directly access to the topics and respective links of MCQs. Moreover, to make learning smooth and efficient, all the questions come with their supportive solutions to make utilization of time even more productive. Students will be covered for all their studies as the topics are available from basics to even the most advanced. .

Q1. Which unit is not for length

•  Parsec
•  Light year
•  Angstrom
•  Nano

Solution
(D) Nano

Q2.SI unit of electric intensity is

•  Coulomb
•  Coulomb/m²
•  Newton
•  Newton/ coulomb

Solution
(d) E=F/q = Newton/coulomb

Q3.The thrust developed by a rocket-motor is given by F=mv+A(p₁-p₂), where m is the mass of the gas
ejected per unit time, v is velocity of the gas, A is area of cross-section of the noszzle, p_1∙p_2are the pressures
of the exhaust gas and surrounding atmosphere. The formula is dimensionally

•  Correct
•  Wrong
•  Sometimes wrong, sometimes correct
•  Data is not adequate

Solution
(a) Each of three terms in the given equation has the dimensional formula of force.

Q4. The dimensional formula for impulse is

•  MLT^-2
•  MLT^-1
•  ML² T^-1
•  M² LT^-1

Solution
(b) Impulse =Force ×Time=[MLT^-2 ][T]=[MLT^-1]

Q5. If P represents radiations pressure, c represents speed of light and Q represents radiation
energy striking a unit area per second, the non-zero integers x,y and z
such that P^x Q^y c^z is dimensionless, are

•  x=1,y=1,z=-1
•  x=1,y=-1,z=1
•  x=-1,y=1,z=1
•  x=1,y=1,z=1

Solution
  (b) By substituting the dimension of given quantities [ML^-1T^-2 ]^x [MT^-3 ]^y [LT^-1 ]^z=[MLT]⁰
By comparing the power of M,L,T in both sides
x+y=0 ...(i)
-x+z=0 …(ii)
-2x-3y-z=0 …(iii)
The only values of x,y,z satisfying (i), (ii) and (iii) corresponds to (b)

Q6. Which is not a unit of electric field

•  NC^-1
•  Vm^-1
• JC^-1
•  JC^-1 m^-1

Solution
(c) JC^-1

Q7. The dimensional formula of self-inductance is

•  MLT^-2
•  ML² T^-1 A^-2
•  ML² T^-2 A^-2
•  ML²T^-2 A^-1

Solution
(c) Energy E=1/2 LI²⇒[L]=([E])/[I]² =([ML² T^-2])/([A²])=[ML² T^-2 A^-2]

Q8. The unit of self-inductance is

•  Weber ampere
•  Weber^-1 ampere
•  Ohm second
•  Farad

Solution
(c) The magnitude of induced emf is
|ε|=L dI/dt or L=|ε|dt/dI
L=(volt×second)/ampere=ohm second

Q9. Consider a new system of units in which c(speed of light in vacuum), h(Planck’s constant)
and G(gravitational constant)are taken as fundamental units. Which of the following would
correctly represent mass in this new system?

•  √(hc/G)
•  √(Gc/h)
•  √(hG/c)
•  √hGc
Solution
(a) [h]=[ML² T^-1]
[c]=[LT^-1]
[G]=[M^-1 L³ T^-2]

Q10. The dimensional formula for the modulus of rigidity is

•  ML² T^-2
•  ML^-1 T^-3
•  ML^-2 T^-2
• ML^-1 T^-2

Solution
(d) Modulas of rigidity=(Shear stress)/(Shear strain)=[ML^-1 T^-2]