Physics

Q71.

If force ( $F$ ), velocity ( $\mathrm{v}$ ), and time ( $T$ ) are taken as fundamental units, the dimensions of mass will be:

Q72. If energy $(E),$ velocity $(v)$ and time $(T)$ are chosen as the fundamental quantities, the dimensional formula of surface tension will be:

Q73.

If dimensions of critical velocity ${v_c}$ of a liquid flowing through a tube are expressed as $\eta^{x}\rho^yr^{z}$ , where $\eta, \rho~\text{and}~r$ are the coefficient of viscosity of the liquid, the density of the liquid, and the radius of the tube respectively, then the values of ${x},$ ${y},$ and ${z},$ respectively, will be:

Q74.

Planck’s constant ( $h$ ), speed of light in the vacuum ( $c$ ), and Newton’s gravitational constant ( $G$ ) are the three fundamental constants. Which of the following combinations of these has the dimension of length?

Q75.

A physical quantity of the dimensions of length that can be formed out of  $c, G,~\text{and}~\dfrac{e^2}{4\pi\varepsilon_0}$ is:
( $c$ is the velocity of light, $G$ is the universal constant of gravitation and $e$ is charge)

Q76. A student measured the diameter of a small steel ball using a screw gauge of least count $0.001$ cm. The main scale reading is $5$ mm and zero of circular scale division coincides with $25$ divisions above the reference level. If the screw gauge has a zero error of $-0.004$ cm, the correct diameter of the ball is:

Q77.

The main scale of a vernier calliper has $n$ divisions/cm. $n$ divisions of the vernier scale coincide with $(n-1)$ divisions of the main scale. The least count of the vernier calliper is:

Q78.

In an experiment, the percentage errors that occurred in the measurement of physical quantities $A,$ $B,$ $C,$ and $D$ are $1\%$ , $2\%$ , $3\%$ , and $4\%$  respectively. Then, the maximum percentage of error in the measurement of $X,$ where  $X=\frac{A^2 B^{\frac{1}{2}}}{C^{\frac{1}{3}} D^3}$ , will be:

Q79. The unit of thermal conductivity is:

Q80.

Time intervals measured by a clock give the following readings: 
$1.25~\text{s},~1.24~\text{s}, ~1.27~\text{s},~1.21~\text{s},~1.28~\text{s}.$  
What is the percentage relative error of the observations?