Inside a horizontally moving box, an experimenter finds that when an object is placed on a smooth horizontal table and is released, it moves with an acceleration of $10\,m / s ^2$. In this box if $1\,kg$ body is suspended with a light string, the tension in the string in equilibrium position (w.r.t. experimenter) will be$.........\,N$ (Take $g =10\,m / s ^2$ )

Two persons are holding a rope of negligible weight tightly at its ends so that it is horizontal. A $15\, kg$ weight is attached to the rope at the mid-point, which now no longer remains horizontal. The minimum tension required to completely straighten the rope is

For given systen ${\theta _2}$ ....... $^o$ 

Which force act on body first action or reaction ?

Give the magnitude and direction of the net force acting on a stone of mass $0.1\; kg$,

$(a)$ just after it is dropped from the window of a stationary train,

$(b)$ just after it is dropped from the window of a train running at a constant velocity of $36 \;km/h$,

$(c)$ just after it is dropped from the window of a train accelerating with $1\; m s^{-2}$,

$(d)$ lying on the floor of a train which is accelerating with $1\; m s^{-2}$, the stone being at rest relative to the train.

Neglect air resistance throughout.

An object of mass $5\, kg$ is thrown vertically upwards from the ground. The air resistance produces a constant retarding force of $10\, N$ throughout the motion. The ratio of time of ascent to the time of descent will be equal to $\left[\right.$Use $g =10 \,ms ^{-2}]$