$A$ ball is thrown upward from the top of a building at an angle of $30^{\circ}$ to the horizontal with an initial speed of $15 \,ms^{-1}$. If the ball hits the ground after $3 \,s$, then the height of the building is (acceleration due to gravity $= 10 \,ms^{-2}$): (in $\,m$)

$A$ fighter plane is flying horizontally at a height of $250\ m$ from the ground with a constant velocity of $500\ m/s$. It passes exactly over a cannon which can fire a shell at any time in any direction with a speed of $100\ m/s$. Find the duration of time for which the plane is in danger of being hit by a cannon shell.

$A$ ball is rolled off the edge of a horizontal table at a speed of $4\, m/s$. It hits the ground after $0.4\, s$. Which statement given below is true?

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 $30^{\circ}$ to the horizontal. The ball will hit the ground in time ........ $s$ (Take $g = 10 \ m/s^2$)

$A$ particle is dropped from a height of $20\,m$ above horizontal ground. Due to wind,the particle experiences a constant horizontal acceleration of $6\,m/s^2$. Find the horizontal displacement of the particle when it reaches the ground.

$A$ bomber plane moves horizontally with a speed of $500 \ m/s$ and a bomb released from it strikes the ground in $10 \ s$. The angle with the horizontal at which it strikes the ground will be $(g = 10 \ m/s^2)$.