Explanation:
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Missing part in the text: "...the charges are <span>separated by a distance of 30.0 cm."
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Solution:
The point midway between the two charges is located 15.0 cm from one charge and 15.0 from the other charge. The electric field generated by each of the charges is

where
ke is the Coulomb's constant
Q is the value of the charge
r is the distance of the point at which we calculate the field from the charge (so, in this problem, r=15.0 cm=0.15 m).
Let's calculate the electric field generated by the first charge:

While the electric field generated by the second charge is

Both charges are positive, this means that both electric fields are directed toward the charge. Therefore, at the point midway between the two charges the two electric fields have opposite direction, so the total electric field at that point is given by the difference between the two fields:
Answer:
The density of balsa wood is about 170 kg/m^3.
Explanation:
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Answer:
It sticks to the wall due to electrostatics.
Explanation:
When pam rubs a balloon against his hair, and holds it up against the wall, he is basically adding a surplus of electrons which are negative charges to the surface of the balloon.
This motion would make the wall the more positively charged than the balloon. Therefore, when the two charges come in contact with each other, the balloon will stick to the wall because of the rule in electrostatics that opposite charges attract each other.
The spring's elastic potential energy is converted into elastic potential energy of the boy.
Potential energy = elastic energy
mgh = 1/2 kx²
k = (2 * 25 * 9.81 * 0.5) / 0.4²
k = 1533 N/m
We will apply
2as = v² - u², with u = 0
a = F/m
F = kx
a = kx/m
v = √(2 x 0.4 x (0.4 x 1533 / 25))
v = 4.43 m/s