Question

Review 1 Constants A0.018 g plastic bead from a hread. Another the point where the thread is distance r4 cm as shown in (Figure 1) Correct Part B use your tee-body diagram and Physics 151 techniques to ind the magnitude of the electric force bethween the two charped Express your answer using three significant gures Figure 1o1 View Available Hinns Part C Complote previous parts) 3

Answer 1

T = tension force in the thread

m = mass of the bead = 0.018 g = 0.018 x 10^-3 kg

$\theta$ = angle of thread with the vertical = 28 deg

Along the vertical direction , force equation is given as

T Cos$\theta$ = mg                                                               eq-1

Along the horizontal direction , force equation is given as

T Sin$\theta$ = F_e                                                               eq-2

dividing eq-1 by eq-2

T Cos$\theta$/(T Sin$\theta$ ) = mg / F_e

F_e = mg tan$\theta$

electric force between the beads is given as

F_e = k q²/r²

hence

k q²/r² = mg tan$\theta$

(9 x 10⁹) q²/(0.04)² = (0.018 x 10^-3) (9.8) tan28

q = 4.1 x 10^-9 C