physics
posted by VJC .
On planet Tehar, the acceleration of gravity is the same as that on Earth but there is also a strong downward electric field with the field being uniform close to the planet's surface. A 2.16 kg ball having a charge of 4.80 uC is thrown upward at a speed of 21.0 m/s and it hits the ground after an interval of 3.63 s. What is the potential difference between the starting point and the top point of the trajectory?

The ball's acceleration downward is given by
a * (3.63/2 s) = 21.0 m/s
a = 11.57 m/s^2
Since g = 9.81 m/s^2, the downward acceleration due to electrostatic force is 1.76 m/s^2
The potential difference V due to electrostatic force at the top of the trajectory is given by
M*1.76* H = Q*V
Solve for V. 
what is H?