What are the three defining features of a planet?

An object moves from position +34m to the position -15m in 15 seconds. what is the total displacement? what is the total velocity?

The electric field between square plates of a parallel-plate capacitor has magnitude e. the potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. the magnitude of the electric field between the plates is now equal to a)e b)e/4 c)e/2 d)4e e)2e

Scientific models are based on current knowledge, which can limit their effectiveness when new discoveries are made.