Why is it safe to stick your tongue on a wooden pole on a cold winter day, but not on a metal pole?

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?

Place me with this question is my last question

Give one example to show that when substances are mixed,it may result in a chemical or a physical change depending on the conditions.