$A$ coin is tossed $n$ times. The probability of getting a head at least once is greater than $0.8$. Then,the least value of such $n$ is:

Which of the following substances is known as $Oil$ $of$ $Wintergreen$?

$A$ ball is thrown upward with an initial velocity $V_0$ from the surface of the earth. The motion of the ball is affected by a drag force equal to $m \gamma v^2$ (where $m$ is the mass of the ball,$v$ is its instantaneous velocity,and $\gamma$ is a constant). The time taken by the ball to rise to its zenith is:

Using the digits $0, 2, 4, 6, 8$ not more than once in any number,the number of $5$-digit numbers that can be formed is:

The outer and inner radii of a hollow cylinder are $(4.23 \pm 0.01) \text{ cm}$ and $(3.89 \pm 0.01) \text{ cm}$ respectively. What is the thickness of the wall of the cylinder?

The average degree of freedom per molecule of a gas is $6$. The gas performs $25 \, J$ of work while expanding at constant pressure. The heat absorbed by the gas is ...... $J$.