If i drill a hole through the center of the earth that cross the entire planet and then i drop a ball into the hole:

1. What is going to be the speed of the ball at the other end of the planet?

2. How much time is going to take the ball of going from one end to another?

Ok, I have:

Mass of Earth= 5.974 * 10 ^24 Kg

R of Earth = 6. 374 * 10 ^ 6 m

G = 6.67 * 10 ^ -11

diameter of Earth = 1.27 *10^7 m

I need to know the speed the ball use to go from one end of the hole to the other end. I thought the speed was 0 m/s but i think i'm wrong.

Should i use [tex]V= \sqrt {2gd} [/tex] ?

Now i have to look for the time it takes the ball to travel from one point to the other. So the ball is going to pass Earth's core.

One point i want to clear is that r = R.

The proffesor told me that we need to use earth's diameter to find time.

If there is something wrong with something i said, please correct me.

I'm lost, please help.