Conductors have many free electrons
insulators have few free electrons
conductors are ideal for electrical wiring
Answer:
a) negative charges are transferred from the rod to the silk.
Explanation:
Only negative charge are transfered by electrons.
Rubbing the glass rod with the silk cause electrons to flow from the glass rod to the silk. This leaves the glass rod with a positive charge.
Let N be the normal force that forces the person against the wall.
Then u N = m g is the frictional force supporting the person's weight
and N = m g / u
also, N = m v^2 / R is the normal force providing the centripetal acceleration
So, m g / u = m v^2 / R
v^2 = g R / u
since v = 2 pi R T
4 pi^2 R^2 T^2 = g R / u and T^2 = g / (4 u pi^2 R)
T = 1/ (2 pi) (g /(u R))^1/2 = .159 * (9.8 m/s^2 / (.521 * 4.4 m)) ^1/2
T = .68 / s
Do you see any thing wrong here?
T should have units of seconds not 1 / seconds
v should be 2 * pi * R / T where T is the time for 1 revolution
So you need to make that correction in the above formula for v.
Answer:
The correct answer is H ÷ ¹/₂T
Explanation:
The formula for velocity is distance covered ÷ time.
Neglecting air resistance;
If the ball's time of overall time flight is T, the time it will take for the second half/return trip is ¹/₂T.
If the ball's maximum height above its released point is H, the height will also be the distance it covered for the second part of the trip since the student caught the ball in the exact same place the ball was thrown. Hence, the distance for the second half of the trip will be H.
Since velocity = distance/time
The average velocity during the second half of the trip will be = H ÷ ¹/₂T
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