Answer:
The torque about the origin is 
Explanation:
Torque
is the cross product between force
and vector position
respect a fixed point (in our case the origin):

There are multiple ways to calculate a cross product but we're going to use most common method, finding the determinant of the matrix:
![\overrightarrow{r}\times\overrightarrow{F} =-\left[\begin{array}{ccc} \hat{i} & \hat{j} & \hat{k}\\ F1_{x} & F1_{y} & F1_{z}\\ r_{x} & r_{y} & r_{z}\end{array}\right]](https://tex.z-dn.net/?f=%20%5Coverrightarrow%7Br%7D%5Ctimes%5Coverrightarrow%7BF%7D%20%3D-%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D%20%5Chat%7Bi%7D%20%26%20%5Chat%7Bj%7D%20%26%20%5Chat%7Bk%7D%5C%5C%20F1_%7Bx%7D%20%26%20F1_%7By%7D%20%26%20F1_%7Bz%7D%5C%5C%20r_%7Bx%7D%20%26%20r_%7By%7D%20%26%20r_%7Bz%7D%5Cend%7Barray%7D%5Cright%5D%20)



Answer:
I think the answer is
C) iron nails are attracted towards all materials
Answer:
Explanation:
Q₁ = 20 X 10⁻⁶ C
Q₂ = -45 X 10⁻⁶ C
d is required distance.
F = Force between the = 7 N
F = k x Q₁ X Q₂ / d²
d² = k x Q₁ X Q₂ / F = 20 X 45 X 10⁻¹² X 9 X 10⁹ /7
=1.157
d = 1.075 m
The first object is also negatively charged that is why people say opposites attract. have a good day!