Answer:
Total energy = 1000J
KE = 500J
PE = 500J
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
"The connective tissue that's found between bones."
An example would be between the vertabrae in the spine.
Like the other (inappropriate) answer said, a ligament is what attches muscles and bones.
Also, the tissue inside of bones is bone marrow.
If you know that, you can take out those two options (Option 1 and 3)
Explanation:
It took 
for the sound to reach the 1st wall and at the same time time, the same sound took 
to reach the 2nd wall. Assuming that the sound travels at 343 m/s, then let 
be the distance of the person to the 1st wall and 
be the distance to the 2nd wall. So the distance between the walls X is
Electronic signals are converted into a 'ray of light' -
