Positive - Friction allows us to create heat in a desperate situation, like being lost in the woods. If we didn't have friction, we would probably freeze to death.
Negative - Friction can also cause unwanted fires, such as forest fires. If friction didn't exist, we wouldn't have these.
Done I don't know answer of this question or this photo is the answer can you tell me
P=w/t
w=15
t=3
therefore, 5 watts (b)