An electron has a negative charge. Hope this helps.
Answer:

Explanation:
For the simple pendulum problem we need to remember that:
,
where
is the angular position, t is time, g is the gravity, and L is the length of the pendulum. We also need to remember that there is a relationship between the angular frequency and the length of the pendulum:
,
where
is the angular frequency.
There is also an equation that relates the oscillation period and the angular frequeny:
,
where T is the oscillation period. Now, we can easily solve for L:

Two fat black arrows are swimming along together, when they see a single skinny black arrow coming toward them. They are afraid of strangers, and they know that the skinny one must be mean and tough if it's not afraid to travel alone. So they turn to the side and get out of the skinny arrow's way.
Answer:
The maximum electric field strength = 0.01 V/m
Explanation:
Given
ΔV(max) = 4.00 mV = 0.004 V
d = 0.400 m
f = 1.00 Hz
Maximum electric field = (maximum potential)/(length)
Maximum electric field = E(max)
Maximum potential = 4.00 mV = 0.004 V
Length = 0.400 m
E(max) = (0.004/0.4) = 0.01 V/m
Hope this Helps!!!