Answer:
1/3
Explanation:
We can solve the problem by using the lens equation:

where
f is the focal length
p is the distance of the object from the lens
q is the distance of the image from the lens
Here we have a divering lens, so the focal length must be taken as negative (-f). Moreover, we know that the object is placed at a distance of twice the focal length, so

So we can find q from the equation:

Now we can find the magnification of the image, given by:

C
Explanation:
This is because the other variables in the other choices are relative to different observers and hence are not good to use in an experiment because there will be a lot of inherent bias by the person conducting the experiment For example how one person views how strong or beautiful the maple or oak looks may be different from how another person perceives the same.
However, weight is an absolute SI unit and does not vary from experiment to experiment. It is, therefore, a non-biased variable to use in the experiment and determine which wood between oak and maple can hold more weight.
Answer:
Resistance in the flash tube, 
Explanation:
It is given that,
Speed of the bullet, v = 500 m/s
Distance between one RC constant, d = 1 mm = 0.001 m
Capacitance, 
The time constant of RC circuit is given by :

R is the resistance in the flash tube
..........(1)
Speed of the bullet is given by total distance divided by total time taken as :




Equation (1) becomes :


So, the resistance in the flash tube is
. Hence, this is the required solution.
Because it on by it's self floating around not forming part of something