Question

You hold a ruler that has a charge on its tip 2 cm above a small piece of tissue paper to see if it can be picked up. The ruler has −14 µC of charge. The tissue has 3 g of mass. What is the minimum charge required to pick up the tissue paper?

Answer 1

Explanation:

It is known that the relation between force and mass is as follows.

                            F = mg .......... (1)

where,    F = force

              m = mass

              g = acceleration due to gravity

Also,     F = $K\frac{q_{1}q_{2}}{r^{2}}$ .......... (2)  

Therefore, equating equations (1) and (2) as follows.

               $K\frac{q_{1}q_{2}}{r^{2}}$ = mg

Putting the given values into the above formula as follows.

              $K\frac{q_{1}q_{2}}{r^{2}}$ = mg

            $9 \times 10^{9} \times \frac{-14 \times 10^{-6} \times q_{2}}{(0.02)^{2}}$ = 3 g \times 9.8[/tex]

             $q_{2} = 9.3 \times 10^{-3}$ C

Therefore, the minimum charge required to pick up the tissue paper is $9.3 \times 10^{-3}$ C.