In which of the following cases the net force is zero .

Options

A. a drop of rain falling down with terminal velocity
B. a cork of mass `20g` floating in water
C. a car moving with constant speed of `60km//h` on a rough road
D. in a tug of war game if one team applies more force than other

Answer

a,b,c

Explanation

If a rain drop falls with terminal velocity
weight = upthrust + viscous drog `:. F _("net") = 0`
For a cork floating in water
weight = upthrust `:. F_("net") =0`
In case of constant speed of a car, `a =0`
In a tug of war game if one team applies more force than other then net force will be the resultant of two forces Which will not be zero
`F _("net") ne 0` .