To make sure that we have enough resourses to sustain ourselves. You see, if we use up, say, all water on earth, then obviously we won't have any more and we'll die.
The answer is option D)
this is because the heat radiated by the flame is mostly absorbed by the air surrounding it, so the air becomes hot and its density decreases (because of expansion), therefore it goes up and it is replaced by cooler air. since all of the hot air flies up, non goes side ways to heat up the match stick, hence it remains cool and does not light up.
option A) also sounds correct, but it isn't. this is because the flame IS hot enough to burn the match stick, it's just that the match stick is positioned the wrong way
Answer:
b) 900 W
Explanation:
The breaker trips when the current is equal to 20 A. The power (P) is the ddp (V) multiplied by the current. So, for the electric heater, the current is:
P = V*i
1500 = 120*i
i = 12.5 A
So, to become in 20 A, it's needed 7.5 A, which must come from the hairdryer. Its power must be:
P = 120*7.5
P = 900 W