Answer:
Total energy = 1000J
KE = 500J
PE = 500J
Step-by-step explanation:
As you may know, the equation for gravitational potential energy is mgh (weight x height)
If the skateboard is halfway down, that means it is at half the height. As the skateboard speeds up (as it goes downward), the potential energy becomes kinetic energy. Since it has 500J of kinetic energy at half way down, it means it had double that amount of Potential energy at the top (1000J). Since half of that became kinetic energy, there is only 500J of PE left.
Total energy = KE + PE = 1000J
KE = 500J
PE = 500J