If the overbridge is concave instead of being convex,the thrust on the road at the lowest position will be

$A$ body of mass $2 \ kg$ is acted upon by two forces each of magnitude $1 \ N$ and inclined at $60^{\circ}$ with each other. The acceleration of the body in $m/s^2$ is $[\cos 60^{\circ}=0.5]$

$A$ $100 \, kg$ gun fires a ball of $1 \, kg$ horizontally from a cliff of height $500 \, m$. It falls on the ground at a distance of $400 \, m$ from the bottom of the cliff. Find the recoil velocity of the gun. (Acceleration due to gravity $g = 10 \, m/s^2$) (in $, m/s$)

$A$ block $A$ with mass $100\, kg$ is resting on another block $B$ of mass $200\, kg$. As shown in the figure,a horizontal rope tied to a wall holds block $A$. The coefficient of friction between $A$ and $B$ is $0.2$,while the coefficient of friction between $B$ and the ground is $0.3$. The minimum required force $F$ to start moving block $B$ will be ........ $N$.

If the net force on a system is zero,then:

$A$ balloon of mass $m$ is descending down with an acceleration $\frac{g}{2}$. How much mass should be removed from it so that it starts moving up with the same acceleration?