From the top of a tower of height $40\, m,$ a ball is projected upwards with a speed of $20\, m/s$ at an angle $30^o$ to the horizontal. The ball will hit the ground in time ........$s$ (Take $g = 10\, m/s^2$)

An aeroplane is flying at a constant horizontal velocity of $600\, km/hr $ at an elevation of $6\, km$ towards a point directly above the target on the earth's surface. At an appropriate time, the pilot releases a ball so that it strikes the target at the earth. The ball will appear to be falling

Two paper screens $A$ and $B$ are separated by distance $100 \,m$. A bullet penetrates $A$ and $B$, at points $P$ and $Q$ respectively, where $Q$ is $10 \,cm$ below $P$. If bullet is travelling horizontally at the time of hitting $A$, the velocity of bullet at $A$ is nearly .......... $m / s$

The maximum range of a gun on horizontal terrain is $16 \,km$. If $g = \;10m/{s^2}$. What must be the muzzle velocity of the shell ......... $m/s$

A ball of mass $0.2 \ kg$ rests on a vertical post of height $5 m$. A bullet of mass $0.01 \ kg$, traveling with a velocity $V / s$ in a horizontal direction, hits the centre of the ball. After the collision, the ball and bullet travel independently. The ball hits the ground at a distance of $20 \ m$ and the bullet at a distance of $100 \ m$ from the foot of the post. The initial velocity $V$ of the bullet is