Answer:
Gravity is the centripetal force when the moon orbits the earth.
<em>Energy</em><em> </em><em>can</em><em> </em><em>neither </em><em>be</em><em> </em><em>created </em><em>nor</em><em> </em><em>be</em><em> </em><em>destroyed</em><em> </em><em>but</em><em> </em><em>can</em><em> </em><em>be</em><em> </em><em>converted</em><em> </em><em>from</em><em> </em><em>one</em><em> </em><em>form</em><em> </em><em>to</em><em> </em><em>another </em><em>.</em>
Answer:
Same direction: t=234s; d=6.175Km
Opposite direction: t=27.53s; d=0.73Km
Explanation:
If the automobile and the train are traveling in the same direction, then the automobile speed relative to the train will be
(<em>the train must see the car advancing at a lower speed</em>), where
is the speed of the automobile and
the speed of the train.
So we have
.
So the train (<em>anyone in fact</em>) will watch the automobile trying to cover the lenght of the train L at that relative speed. The time required to do this will be:

And in that time the car would have traveled (<em>relative to the ground</em>):

If they are traveling in opposite directions, <u>we have to do all the same</u> but using
(<em>the train must see the car advancing at a faster speed</em>), so repeating the process:



Answer:
The second trumpeter will be playing at frequency = 515 Hz
Explanation: Given that the note sounds lower and they can hear 20 beats in 4.0 s.
Beat frequency = 20/4 = 5 Hz
Beat frequency = F2 - F1
5 = 520 - F1
F1 = 520 - 5
F1 = 515 Hz
Since the note sound lower, the second trumpeter will be playing at 515 Hz frequency