1. Two of the 4 fundamental forces:
1. The _____________________ force, Fg, between 2 masses:
Fg =
…is always ______________________
…is ___________________________ to the masses
…is ______________proportional to ____________ of r
…is _______________ , which can be seen because
the constant G = __________________________ is
very _______________
2. The _______________________ force, Fe, between two charges
Fe =
???

2. separated by a distance…
Suppose two charges q1 and q2 repel each other with an
electrical force Fe=___. The following experiments are done:
Exp. #
using….
and….
separated by a distance…
new Fe 1 q1
2q2 2
3q1 q2 3
2q1
3q2 4 5 6
What can you conclude about the form of the electrical force?
It is directly proportional to the _____________ on each object,
and ___________ proportional to the ____________________
_______________________________

3. Coulomb’s Law: The electrostatic force, Fe, between
two charges q1 and q2 separated by a center-to-center
distance r is… q1 q2 r
Fe =
where k = ________________________________
= ________________________________
________________________________

4. Note:
Fe is… …directly proportional to ____________
…and inversely proportional to ______
2. Fe is ___________________ if the charges are “opposite”
and_____________________ if the charges are “like”
3. Fe is ___________stronger than the gravitational force
because ________ is ____________________ than ______.
4. Fe is an ________________________________force.

5. Ex: Find the electrical force between two charges
q1 = +3.4 x 10-6 C and q2 = -1.7 x 10-4 C whose centers
are separated by a distance of 2.5 x 10-2 m.
Fe =
Fe =
Fe =
Is the force attractive or repulsive?
Which charge exerts a stronger force?
If released from rest, which would accelerate more?
You can’t tell, since the masses are not given.

6. Ex: Two neutral masses:
The same two masses with like charges:
The same two masses but with opposite charge:

7. Ex: An analogy between gravity and the electrical force.
planet
___________
holds the
planets to
the Sun (S): S
electron
The ____________
force binds
electrons to
the nucleus (N): N

8. But, orbiting electrons _________________________ Why?
1. Electrons in circular orbits ___________________.
2. Accelerating charges ________________________
3. Therefore, orbiting electrons would ________ energy
and _________________________________ and all matter
would ___________________in a fraction of a second
A new theory was needed. This theory, called ____________
___________________ , was developed. It says that:
1. The electron ________________________ , but
__________________________________ orbit.
2. The “orbit” only tells you where the electron
is ____________________ to be found or the
_____________________ of finding it somewhere!