An iron block is dropped into a deep well. The sound of the splash is heard after $4.23 \, s$. If the depth of the well is $78.4 \, m$,find the speed of sound in air in $m/s$ $\left(g = 9.8 \, m/s^2\right)$.

$A$ spherical insulating ball and a spherical metallic ball of the same size and mass are dropped from the same height. Choose the correct statement out of the following: {Assume negligible air friction}

The time of flight of a vertically projected stone is $8 \,s$. The position of the stone after $6 \,s$ from the ground is (Acceleration due to gravity $= 10 \,m/s^2$). (in $\,m$)

$A$ body falls freely for $10 \ s$. What is its average velocity during this journey (in $m/s$)? (Take $g = 10 \ m/s^2$)

$A$ stone falls freely such that the distance covered by it in the last second of its motion is equal to the distance covered by it in the first $5 \,s$. It is in air for....... $s$.

$A$ ball is thrown vertically upwards with a velocity of $20 \; m s^{-1}$ from the top of a multistorey building. The height of the point from where the ball is thrown is $25.0 \; m$ from the ground. How high will the ball rise above the point of projection (in $; m$)? Take $g = 10 \; m s^{-2}$.