What subatomic particle has a nuetral charge?

Ineed the answers for these promblems i have

Ablock having mass m slides down an inclined plane. the force of friction between the block and the inclined plane is f, the block's weight is m g, and the normal force is n. (a) draw a free – body force diagram showing the forces acting on the block. (b) write down all relevant newton’s equations for a given situation.

The buildup of charges on an object is called