No one has actually seen any other layers beneath the surface of the Earth. A: True
B: False

How many excess electrons must be present on each sphere if the magnitude of the force of repulsion between them is 4.57×10−21 newtons?

1. do the particles in the medium material move in the same direction of the wave or at opposite direction to the wave? explain your answer. 2. by inputting more energy into the wave, i.e a large shake of the spring, which wave property also increases? 3. are there forces of friction acting while a wave is passing through a medium?

Ineed the answer to question 9 and 10