Based on the given, this is probably a gravitational potential energy problem (PEgrav). The formula for PEgrav is:
PEgrav = mgh
Where:
m = mass (kg)
g = acceleration due to gravity
h = height (m)
With this formula you can derive the formula for your unknown, which is mass. First put in what you know and then solve for what you do not know.

![30J=m(10)(10[tex] \frac{30}{100} =m](https://tex.z-dn.net/?f=30J%3Dm%2810%29%2810%5Btex%5D%20%5Cfrac%7B30%7D%7B100%7D%20%3Dm)
)[/tex]
Do operations that you can with what is given first.

Transpose the 100 to the other side of the equation. Do not forget that when you transpose, you do the opposite operation.
m = 0.30kg
The acceleration is 
Explanation:
We can solve the problem by applying Newton's second law of motion: in fact, the net force acting on an object is equal to the product between the mass of the object and its acceleration. Therefore we can write:

where:
is the resultant force acting on the object
m is its mass
a is its acceleration
In this problem, we have the following forces acting on the system:
(forward)
(backward)
So, Newton's second law can be rewritten as:

where:
m = 1050 kg is the mass of all the students
Solving the formula for a, we find the acceleration of the system:

Learn more about Newton's second law:
brainly.com/question/3820012
#LearnwithBrainly
There's nothing on the list you provided that's related to Coulomb's Law.
Answer:
The time taken for the light to travel from the earth to the sun = 496.67 seconds
Explanation:
Estimated distance of the earth to the sun = 149000000km
Speed of light = 300000km/s
Time taken for the light to travel from the sun to the earth = ?
Speed = Distance/time
time = Distance/speed
time = 149000000/300000
time = 496.67 s
The time taken for the light to travel from the earth to the sun = 496.67 seconds