A weight can be hung in any of the following four ways by string of same type. In which case is the string most likely to break?

If an inclined plane is made slowly horizontal by reducing its inclination with horizontal, the component of weight parallel to the plane of block resting on the inclined plane

The horizontal acceleration that should be given to a smooth inclined plane of angle $sin^{-1}\, (1/l)$ to keep an object stationary on the plane relative to the inclined plane is

A dynamometer $D$ is attached to two blocks of masses $6 \,kg$ and $4 \,kg$ as shown in the figure. The reading of the dynamometer is ............ $N$

If net force on a system is zero then

Give the magnitude and direction of the net force acting on

$(a)$ a drop of rain falling down with a constant speed,

$(b)$ a cork of mass $10\; g$ floating on water,

$(c)$ a kite skillfully held stationary in the sky,

$(d)$ a car moving with a constant velocity of $30\; km/h$ on a rough road,

$(e)$ a high-speed electron in space far from all material objects, and free of electric and magnetic fields.