# physics

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PLEASE HELP!! I HAVE A TEST TOMORROW!!

if Q=30 uC, q=5.0 uC, and d=30cm, what is the magnitude of the electrostatic force on q in N?

(Ke= 8.99 x 10^9 Nm^2/C^2)
(uC= micro coulombs)
(u= 10^-6)

a. 15
b. 23
c. zero
d. 7.5
e 38

i don't know where to start with this problem. i don't even have a formula if there is one.

• physics -

Look up Coulombs law.

http://en.wikipedia.org/wiki/Coulomb%27s_law

• physics -

F = k |Q q|/d^2 Coulomb's Law

k = 9*10^9 Nm^2/C^2

here
F = 9*10^9 (30^10^-6)(5*10^-6)/(0.30)^2
= 1350 *10^-3/(9*10^-2)
= 150*10^-1
=15 N
1350

• physics -

i left out an important drawing, but i cant get it to copy correctly.

'''''''d''''''''''''''' 2d
O<--->O<--------->O
Q'''''''' q'''''''''''''''' 2Q

• physics -

i used the ''''''''' to hold the spaces

• physics -

when i do this problem i keep getting 1.49*10^13 does anyone know where i am going wrong K (30*5)/.3^2. Please email me at burtonjoe72@gmail thx

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