Abook on 2- meter high shelf has 20 joules of potential energy? what is the mass of this book?me.

Using the formula Gravitational Potential Energy (J) = Mass (kg) * Gravity Constant (m/s/s) * Height (m), and assuming that gravity is 9.81 m/s/s, this question becomes very easy to solve.

Simply plug in what we know to the equation, and solve.

20 (J) = x (kg) * 9.81 (m/s/s) * 2 (m)
20/9.81 = x*2
2.0387 = x*2
2.0387/2 = x
1.0193679918 = x

So the answer is 1.0193679918 kilograms, or 1,019.3679918 grams.

Hope that helped!