Going to be honest, I had a really bad Physics 1 professor, came out of the clas

Question

Going to be honest, I had a really bad Physics 1 professor, came out of the class knowing nothing.

Can someone help me with the problem below?

In class we watched a video demonstrating an attraction between a large and small sphere. A single frame of the video is reproduced here. It was postulated in class that the force of attraction being witnessed here is much too strong to be a gravitational attraction. We named this much stronger force the electric force. This postulate, and the resulting need to introduce a new force, can be backed up with some numbers. That's the goal of this problem. Calculate the magnitude of the attractive gravitational force that the large sphere exerts on the small sphere. Use the symbol Fgravity for the magnitude of this force. Calculate the actual force that the large sphere exerts on the small sphere to pull it away from vertical by the angle shown in the diagram. Use the symbol Factual for the magnitude of this force. Draw a conclusion: is the actual force much too large to be due to gravitational attraction ? Answer YES or NO and then support your conclusion by referring to the results of your calculations. All of the physics needed to complete these calculations you learned in first-semester college physics (so you won't find any help in Chapter 21). But you will need some numbers to arrive at quantitative results. It might be helpful to know that the mass and radius of the large sphere are M = 150g and R = 10.0 cm. respectively. The mass and radius of the small sphere are m = 0.0500 g and r = 0.500 cm, respectively. Any other quantities needed can be estimated from the picture and fundamental constants can be found in your textbook.

Explanation / Answer

Let Gravitation force of attraction between the particles be Fg
Fg = GMm/d^2
M -= mass of bigger object
m = mass of smaller ball
G = universal gravitational constant
d = distance between the objects

Given, M = 0.15 kg
m = 0.05*10^-3 kg
d = approximately the radius of larger sphere, R = 0.1 m
G = 6.67*10^-11
so Fg = 50.025*10^-15 N

Now from the diagram, let the angle that the wire makes with the vertical be theta
so, let tensio nin the string be T
Tcos(theta) = mg
Tsin(theta) = F ( F is force of attraction due to bigger ball on the smaller ball)

so, tan(theta) = F/mg
F = mg*tan(theta) = 0.05*10^-3*9.81*tan(theta) = 0.0004905 tan(theta)
now from the figure, theta is approxiomately 20 deg
so F = 1.785*10^-4 N

so F > > Fg hence this force is not force of gravitation

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