A particle of mass 1 × 10−5 kg and charge
2 μC moves downward from point A to point
B a distance of 4 m in the earth’s gravita-
tional field. The kinetic energy of the particle
decreases by 4.2 mJ during this movement.
What is the potential difference VB − VA?
The acceleration of gravity is 9.8 m/s2 .
Answer in units of kV

Question

A particle of mass 1 × 10−5 kg and charge
2 μC moves downward from point A to point
B a distance of 4 m in the earth’s gravita-
tional field. The kinetic energy of the particle
decreases by 4.2 mJ during this movement.
What is the potential difference VB − VA?
The acceleration of gravity is 9.8 m/s2 . 
Answer in units of kV

anonymous · Answer

Do you know where to start? 
Perhaps using energy concepts maybe? 
remember electric and gravitational fields are conservative, which means, the total energy of a particle in these fields will ALWAYYYYYYYYYYYYYYYS remain constant!!

anonymous · Answer

I used the equation $$v =(mgd - \Delta K ) / q$$  
and I got an incorrect answer of 2.1 I'm not sure what I did wrong