A ball is shot up from the ground with an initial vertical velocity of 30
m/s. What is the final velocity of the ball right before it returns to the
ground?

wavelength variability is the right one

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.

a skateboard rolling across the street - apex

electrical potential energy =0.072 j

explanation:

electrical potential energy is given by

u= q δv

q= charge=6 c

δv= potential difference and is given by

δv= e d

e= electric field

d= distance=5 mm=0.005 m

δv=2.4 (0.005)=0.012 v

now electric potential energy= u= q δv

u=6 (0.012)

u=0.072 j