The distance from the center of the lens to its principal focus is called the focal length. O A. True
O B. False​

An observer that stands still as the electron moves by him, will observe

Could someone . i have tried to solve myself but my calculation is off

You throw a small rock straight up from the edge of a highway bridge that crosses a river. the rock passes you on its way down, 7.00 s after it was thrown. what is the speed of the rock just before it reaches the water 28.0 m below the point where the rock left your hand? ignore air resistance.