Given
Three 7 ohm resistor are in series.
The battery is V=10V
To find
The equivalent resistance
Explanation
When the resistance are in series then the resistance are added to find its equivalent.
Thus the equivalent resistance is:

Conclusion
The equivalent resistance is 21 ohm
Answer:
The answer is 0.83 seconds.
Explanation:
The formula of free fall is following:

Where g=9.8 m/s^2 and t=2 seconds, the rock takes:

19.6 meters. This is the half distance of the cliff. The whole distance is 39.2 meters. So it takes:

2.83 second to fall down completely. The rock takes the second half of the cliff in 0.83 seconds
The suspended ash made for some some spectacular sunsets! Sulfuric acid was spread worldwide, increasing acidity of rain. Ash deflected energy from the sun, causing a slight drop on global temps for a few years.
Its a thermometer . i hope this helps you