In the ever popular game from the future, Electrodisc, players can score double
ID: 2124784 • Letter: I
Question
In the ever popular game from the future, Electrodisc, players can score double points by pushing a disc into another disc with the electric field generated by a third disc. The discs are by regulation 1 kg. All discs have the same shape and are made of the same conducting material. In the figure below, disc 1 is held in place, and disc 2 is held stationary 3.7 m from disc 1 by a player. The player then releases disc 2. What is the initial magnitude of the acceleration imposed on the second disc? The charge on the first disc is 1.9 mC. The charge on the second disc is 1.1 mC. The charge on the third disc is neutral.
Explanation / Answer
the charge on first disc is q1 = 1.9 mC = 1.9 x 10^-3 C
the charge on second disc is q2 = 1.1 mC = 1.1 x 10^-3 C
the charge on third disc is q3 = 0
the force of repulsion between disc 1 and disc 2 is
F = k x (q1q2/r^2)
where k = (1/4pi x e_o) = 9 x 10^9 Nm^2/C^2 and r is separation distance between the discs
the gravitational force on disc is
Fg = m x a
where m = 1 kg and a is acceleration of disc
here,Fg = F
or m x a = k x (q1q2/r^2)
or a = k x (q1q2/m x r^2)