The temperatures of two bodies measured by a thermometer are $t_1 = 20^{\circ}C \pm 0.5^{\circ}C$ and $t_2 = 50^{\circ}C \pm 0.5^{\circ}C$. The temperature difference and the error therein are:

$A$ student performs an experiment for the determination of $g = \frac{4 \pi^{2} \ell}{T^{2}}$. Given $\ell = 1 \, m$,the student commits an error of $\Delta \ell$. For $T$,the student measures the time of $n$ oscillations using a stopwatch with a least count of $\Delta T$ and commits a human error of $0.1 \, s$. For which of the following data will the measurement of $g$ be the most accurate?

The error in the measurement of force acting normally on a square plate is $3 \%$. If the error in the measurement of the side of the plate is $1 \%$,then the error in the determination of the pressure acting on the plate is (in $\%$)

In an experiment to find acceleration due to gravity $(g)$ using a simple pendulum,the time period of $0.5 \ s$ is measured from the time of $100$ oscillations with a watch of $1 \ s$ resolution. If the measured value of length is $10 \ cm$ known to $1 \ mm$ accuracy,the accuracy in the determination of $g$ is found to be $x \%$. The value of $x$ is:

The energy of a system is given as $E(t) = \alpha^3 e^{-\beta t}$,where $t$ is the time and $\beta = 0.3 \ s^{-1}$. The errors in the measurement of $\alpha$ and $t$ are $1.2 \%$ and $1.6 \%$,respectively. At $t = 5 \ s$,the maximum percentage error in the energy is: (in $\%$)

Out of absolute error,relative error,and fractional error,which has a unit and which has no unit?