In the motion of a projectile moving freely under gravity,which of the following is true?

$A$ particle is thrown with a speed of $12 \, m/s$ at an angle $60^o$ with the horizontal. The time interval between the moments when its speed is $10 \, m/s$ is $(g = 10 \, m/s^2)$.........$s$

If the instantaneous velocity of a particle projected as shown in the figure is given by $v = a \hat{i} + (b - ct) \hat{j}$,where $a, b$,and $c$ are positive constants,the range on the horizontal plane will be

The maximum horizontal range of a projectile is $160 \ m$. When the projectile is thrown with the same speed at an elevation of $30^{\circ}$ from the horizontal,it will reach a maximum height of ......... $m$.

$A$ bullet is fired from a gun at the speed of $280\,m/s$ in the direction $30^{\circ}$ above the horizontal. The maximum height attained by the bullet is $........\,m$ $\left(g=9.8\,m/s^2, \sin 30^{\circ}=0.5\right):-$

If a body projected with a velocity of $19.6 \ m/s$ reaches a maximum height of $9.8 \ m$,then the range of the projectile is (Neglect air resistance). (in $m$)