<span>B. Controls: The known powders attributes are already studied, so the are used as control measures to compare with the findings in the experiment with the unknown powders.</span>
Answer:
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Explanation:
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Answer:
1) 341 Hz
Explanation:
When a string vibrates, it can vibrate with different frequencies, corresponding to different modes of oscillations.
The fundamental frequency is the lowest possible frequency at which the string can vibrate: this occurs when the string oscillate in one segment only.
If the string oscillates in n segments, we say that it is the n-th mode of vibration, or n-th harmonic.
The frequency of the n-th harmonic is given by

where
n is the number of the harmonic
is the fundamental frequency
Here we have:
is the frequency of the 3rd harmonic
So the fundamental frequency is

And so, the frequency of the 2nd harmonic is:

Answer:

Explanation:
The impulse-momentum theorem states the impulse on an object is equal to the change in momentum of that object. Momentum is given by
. Since mass is constant, the train's change in momentum is:
(two significant figures).
Impulse is also given as
, where
is the average force applied and
is change in time. Since
is given as
, we have the following equation:
(two significant figures).