The change in pitch of a train's horn as it passes while you are standing still can be explained by the Doppler effect. The correct option among all the options given in the question is option "A". When the sound source from the horn of the train comes closer, the sound seems to come closer each time a sound wave gets emitted. So it comes closer to us in a bunched form. The reverse happens when the train has just passed with each emitted sound going further and further away. The frequency of the sound seems to get lower as the train moves further away.
Answer:
The net gravitational force on the mass is 
Explanation:
We have by Newton's law of gravity the force of attraction between masses 
Applying vales we get
Force of attraction between 135 kg mass and 38 kg mass is
Force of attraction between 435 kg mass and 38 kg mass is
Thus the net force on mass 38.0 kg is 
Answer:
<em>The number 0.0217 has 3 significant digits</em>
Explanation:
<u>Significant Digits
</u>
These are digits that contribute to the significance of the number. Some rules apply to discard the non-significant digits like:
- Leading zeros
- Trailing zeros (with exceptions)
Our number is 0.0217 has two leading zeros before the 2 because they only occupy space to indicate the order of magnitude of the number. Only the 2,1,7 are significant digits, thus
The number 0.0217 has 3 significant digits
a,b,c is your answer light and sound are not considered matter and heat is energy created from matter and electricity is particles moving basically therefore electricity is matter hope this helps
