Answer:
Explanation:
frequency of whistle = 1.85 x 10² = 185 Hz
frequency of beat heard = 8 beat /s . No of beat produced is equal to difference of frequencies of two sound source . Here difference is created due to Doppler effect . One of the train is moving so it will have apparent frequency which is different one from its original frequency .
When the moving train is approaching the observer , its frequency will be higher . As beat is heard at the rate of 8 beats / s , apparent frequency of approaching train will be 185 + 8 = 193 Hz .
Applying Doppler's formula of apparent frequency ,
193 = 185 x V / ( V - v ) , where V is velocity of sound and v is velocity of train .
193 V - 193 v = 185 V
193 v = 8 V
v = 8 x V / 193
= 8 x 343 / 193
= 14.21 m /s
Second possibility is that apparent velocity is less ie 185 - 8 = 177 Hz
In that case moving train will be moving away from observer . If its velocity be v
177 = 185 x V / ( V + v )
177 V + 177 v = 185 V
v = 8 x 343 / 177
= 15.50 m /s .
<u>Answer:</u>
The acceleration of the plane and the time required to reach this speed is (a)= 7.5 
and time(t) = 20 seconds
<u>Explanation:
</u>
Given data Initial velocity 
= 0
Final velocity (
) = 150 m/second
Distance (d) = 1500 m
We have the formula, 
which gives 
= 0+2a(1500)
22500 = 3000 a
acceleration (a) = 7.5 
150 = 7.5 t
t= 150/7.5 = 20
t = 20 seconds.
That is a lunar eclipse. At night, when the Earth is between the Sun and the moon, the moon would appear to be red. Just for future reference, a solar eclipse is when the Moon is between the Sun and Earth. Speaking of which, check out the solar eclipse this August!
Answer:
100% of the energy entering earth's atmosphere comes from the sun. ~50% of the incoming energy is absorbed by the earth's surface i.e. the land and oceans.
