Speed is how fast you cover a distance.
(distance covered) divided by (time to cover the distance).
Acceleration is any change in your motion ... speeding up,
slowing down, or changing the direction you're headed.
(a) 646.9 Hz
The formula for the Doppler effect is:
where
f = 600 Hz is the real frequency of the sound
f' is the apparent frequency
v = 345 m/s is the speed of sound
is the velocity of the observer (zero since it is stationary at the station)
is the velocity of the source (the train), moving toward the observer
Substituting into the formula,
(b) 20.1 m/s
In this case, we have
f = 600 Hz is the real frequency
f' = 567 Hz is the apparent frequency
Assuming the observer is still at rest,
so we can re-arrange the Doppler formula to find 
, the new velocity of the train:
and the negative sign means the train is moving away from the observer at the station.
Answer:
Option C
Explanation:
v= u + at
20 = 5 + a(5)
15= a(5)
a= 3 m/s²
Force = mass × acceleration
= 10 × 3
= 30 N
<span>Tachyons are studied in an area called particle physics, and I must say this is a bit out of my league, but I'll give you some general thoughts. Tachyons are hypothetical particles resulting from what physicists call a thought experiment. Back in the 1960s, some physicists wondered what would happen if matter could travel faster than the speed of light, something that is supposed to be impossible according to the Theory of Relativity. So these particles may or may not exist because they have not been proven or disproven by real experiment as of yet. What people have done is apply existing formulas to the unique properties of tachyons (like imaginary mass!). What comes out is a particles that go faster when they lose energy with a MINIMUM velocity of the speed of light and a maximum velocity of infinity! Hope that helps Ben, theoretical physics is a weird place and is not too far off from philosophy.</span>
