a. 0.5 T
- The amplitude A of a simple harmonic motion is the maximum displacement of the system with respect to the equilibrium position
- The period T is the time the system takes to complete one oscillation
During a full time period T, the mass on the spring oscillates back and forth, returning to its original position. This means that the total distance covered by the mass during a period T is 4 times the amplitude (4A), because the amplitude is just half the distance between the maximum and the minimum position, and during a time period the mass goes from the maximum to the minimum, and then back to the maximum.
So, the time t that the mass takes to move through a distance of 2 A can be found by using the proportion
and solving for t we find
b. 1.25T
Now we want to know the time t that the mass takes to move through a total distance of 5 A. SInce we know that
- the mass takes a time of 1 T to cover a distance of 4A
we can set the following proportion:
And by solving for t, we find
These actions are an example of feedback.
Given that the room has reached the desired temperature, there is no more need for it to be heated, at least until the temperature drops a bit. This is why the thermostat sends feedback about this situation to the heater, which immediately switches off until it is needed again.
If a new substance suddenly appears that wasn't there originally,
then a chemical change has occurred.
Like for example, (this is the only example I can think of right now):
-- You leave your bicycle outside in the rain, and it gets wet, and
a few days later there's some rust on it.
-- You scrape off some of the rust, take it to school, give it to the
Chemistry teacher, and ask her to analyze it and tell you what it
is. Later that day, she tells you it's a substance called "Iron oxide".
-- Where did that come from ? There was no iron oxide there.
There was only iron in the bicycle, and air, and water.
-- The iron oxide formed from a chemical change when the iron
on the surface of the bike combined with some of the oxygen in
the air, and molecules of a new substance were created. (For
some reason, the presence of water makes this chemical reaction
go faster.)
1.) Power, P = V²/R = 800²/45 = 4.5 W (A).
2.) Six Resistors in Series.
R = R1 + R2 + R3 + R4 + R5 + R6, Since R is the same, R = 20
R total = 6*20 = 120 (D)
3.) It is the current. Series connection is to evaluate current. (B)
