What is lighting in year explaining using the work of van de graaf, what likes charges do and explanaton of what stuff is.

A2k pendulum has a speed of 1 m/s at a height of 1/2 meter

What’s #16 asking me and how do i solve it?

How to tell if two objects are in thermal equilibrium 1.the objects have the same temperature 2.the objects are the same size 3.the objects are touching each other 4.the objects temperatures are changing