3. Other names for S- waves are secondary waves, shear waves, and sometimes elastic S-waves. Other names for P-waves are primary waves and compressional waves.
4. You need 3 stations, because scientists find the difference between the arrival times of the primary and the secondary waves at each of the 3 stations, then the time difference is used to determine the distance of the epicentre from each station. The greater the difference in time, the further away the epicentre is. A circle is drawn around each station, with a radius corresponding to the epicentre’s distance from that station. The point where the three circles meet is the epicentre. If you only had two stations, you could only predict the epicentre, as the point where all three circles meet wouldn’t be complete, you’d have to try and estimate where the third one would intercept. This would greaten the chance of error and isn’t as accurate.
Hope this helps!
Answer:
Current, I = 8 A
Explanation:
We have,
Voltage, V = 160 V
Resistance, R = 20 ohms
It is required to find the current. The relation between current, voltage and resistance is called Ohm's law. It is given as :

I = current

So, the value of current is 8 A.
Answer: 5622.6g
Explanation:
Note: Kf for water is 1.86°C/m.
The simple calculation is in the attachment below.
For a candle to burn, it requires a spark, which provides the activation energy for the oxidation reaction of the hydrocarbon making the candle.
It also requires oxygen to facilitate the oxidation of the hydrocarbon.
Therefore the two main requirements of combustion of a candle are oxygen and a spark (or an initial flame)