Question

Determine the mechanical energy of this object: a 1-kg ball sits on a 10-meter high cliff.

Answer 1

The answer would be 98 J

Answer 2

Answer:

C. 98 J

Explanation:

Mechanical energy is defined as the sum of kinetic energy (K) and potential energy (U):

E = K + U

where

$K=\frac{1}{2}mv^2$ is the kinetic energy, where m is the mass of the object and v its speed

$U=mgh$ is the potential energy, where g is the gravitational acceleration and h the height of the object relative to a reference point

For the object in this problem, the kinetic energy is zero, because it is not moving, so v = 0 and K=0. So the mechanical energy is just given by the potential energy, which is given by:

$E=U=mgh=(1 kg)(9.8 m/s^2)(10 m)=98 J$