A car is driving at a speed of 50 m/s. After 6 seconds he notices a wreck up ahead and slows down to 20 m/s. What is his acceleration

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