Answer:

Explanation:
Suppose the tension in the ribbon is T.
The upwards component of the tension = Tcos13
The horizontal component of the tension = Tsin13
The weight of the medal = mg
In a vertical direction, mg is balanced by Tcos13, so mg=Tcos13, so T = mg/cos13. The horizontal component of T is the force causing m to accelerate.

Substituting T= mg/cos13 gives:

cancels and you have

Answer:
this could be called an open system.
Relation between electrostatic force and distance is inverse square i.e
1
Fα ----
r^2
Hence if r is tripled, new electrostatic force will be 1/9 times old force.
My guess is A. I'm not 100% positive but i'm pretty sure.
Answer:
Answered
Explanation:
The data given in the problem
Diameter of a human pupil=0.007 m=7 mm
Diameter of alien pupil=0.5=500 mm
Here we have to calculate the minimum distance at which the alien can see Betelgeuse i.e. the focal length (or the working distance). For this calculation we assume the eye to be a spherical lens.
The focal length and diameter of the lens are related by the formula
Where r is radius of curvature i.e. d/2
Therefore for the alien, focal length=
=12.5mm=0.0125