A rock is thrown 0.8 meters into the air. Find how fast it was thrown.

3.96 m/s

Explanation:

Given

Rock is thrown to a height of 0.8 m

We know that energy is conserved

Total Energy=kinetic Energy+Potential Energy

At bottom Kinetic Energy is maximum and Potential energy is minimum while at the top potential Energy is maximum and kinetic energy is minimum

Energy at Bottom

Energy at Top

Thus

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .