Answer:
Q = 6.33μC
Explanation:
To find the value of the charge Q you take into account both gravitational force and electric force over each ball. By symmetry you can use the fact that both balls experiences the same forces. Hence you only take into account the forces for one ball for the x component and y component:
M: mass of the ball = 0.09kg
T: tension of the string
F_e: electric force between charges
angle = 45°
The electric force is given by:
Q: charge of the balls
r: distance between balls = 2m
You divide both equation in order to eliminate the tension T:
By doing Q the subject of the formula and replacing you obtain:
hence, the charge of the balls is 6.33μC
Answer:
a) Yes because spiderman isn’t part of the system (the train), so he exerts an external force on the system, causing it to slow. The sign is negative because the train is slowing negative.
b) The train was initially moving, so it had kinetic energy, the energy of movement. There isn’t the same amount anymore because spiderman did work onto the train. Work is defined by the change of kinetic energy of the system, so the train didn’t have the same amount of that type of energy at the end.
I hope this helps! :)
The answer is C in this question.