(a) For the work-energy theorem, the work done to lift the can of paint is equal to the gravitational potential energy gained by it, therefore it is equal to
where m=3.4 kg is the mass of the can, g=9.81 m/s^2 is the gravitational acceleration and 
is the variation of height. Substituting the numbers into the formula, we find
(b) In this case, the work done is zero. In fact, we know from its definition that the work done on an object is equal to the product between the force applied F and the displacement:
However, in this case there is no displacement, so d=0 and W=0, therefore the work done to hold the can stationary is zero.
(c) In this case, the work done is negative, because the work to lower the can back to the ground is done by the force of gravity, which pushes downward. Its value is given by the same formula used in part (a):
Answer:
The charge of each sphere is 
Explanation:
The free body diagram of this question is shown on the first uploaded image
From the question we are told that
The mass of the two sphere is 
The length of the connection is 
The angle between the suspended side is 
At Equilibrium the force acting at the horizontal is = 0N and the net force acting at the vertical is zero
This can be represented mathematically as
For 
=> 
For 
=> 
Now 
Where F is the electrical force which is mathematically represented as
Therefore
Where 
is the distance between the two masses and from the diagram it is
So
making q the subject of the formula
Where k is the Coulomb's constant with a value of 
Substituting values
The negative sign is because we are told from the question that they are negatively charged
Answer is a cut from a knife
C) studying seismic waves
AKA what is studied from earthquakes
