Wo charged spheres are 1.5 m apart and are exerting an electrostatic force (fo) on each other. if the charge on each sphere decreases by a factor of 9, determine (in terms of fo) how much electrostatic force each sphere will exert on the other.

F0 / 81

Explanation:

Let the two charges by Q and q which are separated by d.

By use of coulomb's law

F0 = k Q q / d^2      (1)

Now the charges are decreased by factor of 9.

Q' = Q / 9

q' = q / 9                 (2)

Now the Force is

F' = k Q' q' / d^2

F' = k (Q /9) (q / 9) / d^2

F' = k Q q / 81d^2

F' = F0 / 81      

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards