If a person with a mass of 70 kg is standing on top of a cliff that is 30 meters high, how much gravitational potential energy does the person have, relative to the top of the cliff?

What's the formula for gravitational potential energy? If you don't know it, you may have to actually look in your physics book (gasp!). Once you have the formula, you have all the information you need.

For simple mechanical problems as described by your question the formula for gravitational potential energy is given by [m x g x h]. Where m is defined as the mass of the object. g is the acceleration due to gravity. h is the height of the object (above or below a particular reference level).

To solve the equation in your example, substitute the values given into the formula. Since the values are given in the mks(meters, kilograms, seconds) system, you'll need to find the value of g in that same system. Happy computing ! :)