It a because I learn it in class today
It means they have very high resistance.
High resistance means the power cannot fully pass through the wire. Some of the power is lost in the form of light, heat, etc.
Low resistance means the current fully passes through. The wire would then stay cold and nice.
The distance covered by car is equal to (assuming it is moving by uniform motion) the product between the car's speed and the time of the car ride, 4 h:

where

is the car's speed

is the duration of the car ride
Similarly, the distance covered by train is equal to the product between the train's speed and the duration of the train ride, 7 h:

The total distance covered is S=255 km, which is the sum of the distances covered by car and train:

which becomes

(1)
we also know that the train speed is 5 km/h greater than the car's speed:

(2)
If we put (2) into (1), we find

and if we solve it, we find


So, the car speed is 20 km/h and the train speed is 25 km/h.
Answer:
The charge on the wool after rubbing is - 10 C
Explanation:
Every uncharged body is electrically neutral, if the plastic rod acquires 10 Coulombs of charge after been rubbed with wool, then the wool will be left with an equal but opposite charge. This shows that the initial charge on the wool is 10 protons and 10 electrons and when the plastic acquires 10 C (10 protons), the wool will be left with excess 10 electrons.
Therefore, the charge on the wool after rubbing is - 10 C (negative 10 Coulombs).