Arock at the top of a 30 meter cliff has a mass of 25 kg. calculate the rock’s gravitational potential energy when dropped off the cliff. assuming that energy is conserved and there is no air friction and gravity is 9.8 m/sec., at the bottom of the cliff the rock’s potential energy is completely converted to kinetic energy. use the formula for kinetic energy to calculate the rock’s speed at the bottom of the cliff. show all calculations.

Lets see:-

We have our formula for potential energy, which we are trying to solve for, 

PE = mgh  or  potential energy = mass * gravity * height

So we know that PE all depends on these. 

Height :  30 meters
Mass : 25 kg
Gravity (which is always constant) : 9.8 m/s/s

Now add into formula. 

PE = 25*30*9.8 
PE = 7350 Joules

PE = 7350 Joules

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.