Places of hot climate it is advised that outer walls of houses be painted white. Why?

Aman pushes on a trunk with a force of 250 newtons. the trunk does not move. how much positive work is done on the trunk? 0.0 j -250 j 250 j 125 j

Can someone explain to me how to do this problem ?

Two point charges are on the y axis. a 3.90-µc charge is located at y = 1.25 cm, and a -2.4-µc charge is located at y = −1.80 cm. (a) find the total electric potential at the origin. v (b) find the total electric potential at the point whose coordinates are (1.50 cm, 0). v