21. How far above the surface of Earth does an object need to be so that it weighs half as much as it would normally? [5 marks]23. A proton with a charge of 1.60 x 107" C is shot from plate B toward plate A with a speed of 1.5 x 10 m/s. (= 1.0 x 10* Vim, 4 = 0.0030 m) Draw a picture of situation. [7marks] (a) What 1s the electric potential between the plates? (b) What will the speed of the proton be just before it hits plate A