A car of mass $m$ when passes over top of convex bridge of radius of curvature $r,$ with a velocity $v,$ then the normal force exerted by the bridge on the car is
Zero
$mg$
$mg + \frac{{m{v^2}}}{r}$
$mg - \frac{{m{v^2}}}{r}$
The ends of a rope are held by two men who pulls on it with equal and opposite forces of magnitude $F$ each. Then the tension in the rope is
Ten one-rupeed coins are put on top of each other on a table. Each coin has mass $m$. The reaction of the $6^{th}$ coin (counted from the bottom) on the $7^{th}$ coins is .......... $mg$
Two equal heavy spheres, each of radius $r$, are in equilibrium within a smooth cup of radius $3 r$. The ratio of reaction between the cup and one sphere and that between the two sphere is