To solve this problem it is necessary to apply the concepts related to Dopler's Law. Dopler describes the change in frequency of a wave in relation to that of an observer who is in motion relative to the Source of the Wave.
It can be described as
c = Propagation speed of waves in the medium
= Speed of the receiver relative to the medium
= Speed of the source relative to the medium
Frequency emited by the source
The sign depends on whether the receiver or the source approach or move away from each other.
Our values are given by,
Velocity of car
velocity of motor
Velocity of sound
Frequency emited by the source
Replacing we have that
Therefore the frequency that hear the motorcyclist is 601.7Hz
The activation energy is 10 kJ and the reaction is exothermic.
(a) 1200 rad/s
The angular acceleration of the rotor is given by:
where we have
is the angular acceleration (negative since the rotor is slowing down)
is the final angular speed
is the initial angular speed
t = 10.0 s is the time interval
Solving for 
, we find the final angular speed after 10.0 s:
(b) 25 s
We can calculate the time needed for the rotor to come to rest, by using again the same formula:
If we re-arrange it for t, we get:
where here we have
is the initial angular speed
is the final angular speed
is the angular acceleration
Solving the equation,
<span>a.The hiker had an easy, level trail from 11:00-12:00 and was able to travel the fastest during that time period.---> may be because this was indeed fastest stage
b.The hiker got tired and walked the slowest from 1:00-2:00.---> no, because this was not the slowest stage
c.The hiker stopped for lunch from 11:00-12:00 and that slowed him down.---> no because this was the fastest stage
d.The hiker ended up in the same place that he started.---> no, because the hiker walked more toward east than toward west and more toward south than toward north.
Answer: option a) </span>
