Answer with Explanation:
We are given that
Force acts on a pebble=
N
Position vector=
m
a.We have to find the resulting torque on the pebble about origin.
Torque=
Substitute the values then we get

Torque=
N-m
By using 
b.

Torque about point (2,0,-3)

N-m
It will be a physical change
The question ask to calculate and choose among the following is the distance of the microphone from the left - most speaker in order to pick up the loudest sound and the best answer would be letter C. I hope you are satisfied with my answer and feel free to ask for more if you have questions and further clarifications
A) Net force in component form: 
B) Magnitude of the net force: 316.2, direction: 
Explanation:
A)
The three forces given in this problem are:



The three forces are given in component form, where the components with unit vector i is the component along the x-direction, while the components with unit vector j is the component along the y-direction.
In order to find the net force in component form, we just need to add the components of the three forces along each direction. Therefore:
- Along the x-direction:

- Along the y-direction:

So, the net force in component form is

B)
The magnitude of a vector F is given by Pythagorean's theorem:

where in this problem,
is the x-component
is the y-component
Substituting,

The direction instead is given by

where the negative sign means the direction is below the positive x-axis.
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