الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

Lectures in General Physics
2.10) Four point charges are situated
at the corners of a square of sides a
as shown in the figure 2.10. Find
the resultant force on the positive
charge +q.
- q
a
- q
2.13) Two similar conducting balls of
mass m are hung from silk threads
of length l and carry similar
charges q as shown in the figure
2.11. Assume that θ is so small
that tanθ can be replaced by sinθ.
Show that
⎛ q2
l
2 ⎟ ⎞
x =
⎜
⎝ πε ο
mg ⎠
1 3
+q
a
Figure 2.10
- q
where x is the separation between
the balls (b) If l=120cm, m=10g
and x=5cm, what is q?
2.11) Three point charges lie along
the y-axis. A charge q 1 =-9µC is at
y=6.0m, and a charge q 2 =-8µC is at
y=-4.0m. Where must a third
positive charge, q 3 , be placed such
that the resultant force on it is zero?
L
θ θ
L
2.12) A charge q 1 of +3.4µC is
located at x=+2m, y=+2m and a
second charge q 2 =+2.7µC is
located at x=-4m, y=-4m. Where
must a third charge (q 3 >0) be
placed such that the resultant force
on q 3 will be zero?
+q x
Figure 2.11
+q
Dr. Hazem Falah Sakeek