Velocity = displacement (distance)/time
v=80m/4s
v=20m/s
velocity = 20 meters per second
Answer:
Explanation:
Given:
Charge = <em>q</em>
Electric field strength =
weight of the droplet = <em>mg</em>
The charge is suspended motionless. This is because the electric force on the charge is balanced by the weight of the droplet.
electric force on charged droplet, 
This is balanced by the weight, 
Equating the two:

Not knowing how to convert the type of measurement according to your way of learning from where ever you come from.
Well depending on the speed of both of those things is were the rock will be placed and it also determines how fast can an environment change
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If there was any way to do that, then your teacher wouldn't
need to keep you coming into class every day and doing
homework every night. She could just give you the 3 or 4
paragraphs and a few pictures that you're asking me for,
and bada-bing ! you'd know it !
The time it takes, and the amount of homework it takes, is
EXACTLY the time you spent hearing about it in class.
(Unless you're some kind of genius savant prodigy, which
you're not and I'm not.)