A 700# rock sits atop a 150 foot cliff.

1) If it is pushed off how much kinetic energy is in the rock just before it hits the ground?

2) How much potential energy does it have just before it hits the ground?
On 2 will I use the mgh formula? If so what height do I use?

On 1 , I think I use the formula 1/2mv^2, if that is correct what number do I plug in the v spot?

1. KE=original PE mgh

2. PE at bottom is zero

Ido it reaches 0 even before it makes contact?

To answer your questions:

1) To calculate the kinetic energy of the rock just before it hits the ground, you can use the formula: KE = 1/2 * mv^2, where KE is the kinetic energy, m is the mass of the rock, and v is the velocity of the rock.

To find the velocity of the rock just before it hits the ground, we can use the concept of potential energy being converted into kinetic energy. The potential energy of the rock at the top of the cliff is equal to its gravitational potential energy, which is given by the formula: PE = mgh, where PE is the potential energy, m is the mass of the rock, g is the acceleration due to gravity (approximately 9.8 m/s^2), and h is the height of the cliff.

So, the potential energy of the rock at the top of the cliff is PE = 700 * 9.8 * 150 = 1,029,000 Joules (rounded to the nearest thousand). This potential energy is converted into kinetic energy as the rock falls.

2) Just before the rock hits the ground, all of its potential energy is converted into kinetic energy. Therefore, the potential energy of the rock just before it hits the ground can be considered as zero. This is because the height, h, in the potential energy formula becomes zero when the rock is at ground level.

So, for the second question, the potential energy just before it hits the ground can be considered as zero.

To summarize:
1) The kinetic energy just before the rock hits the ground can be calculated using the formula KE = 1/2 * mv^2, where you'll need to plug in the mass of the rock (m) and the velocity (v) of the rock just before impact.
2) The potential energy just before the rock hits the ground can be considered as zero, as the height (h) in the potential energy formula becomes zero when the rock is at ground level.