Alice drops an apple from a height of 2 m above the ground. Assuming there is no air resistance, what is the speed of the apple when it hits the ground?

Since there is no loss of energy to air resistance and the apple is freely falling under the influence of gravity, this is an example where we can apply the principle of conservation of energy. In the initial state, just before it is released, the apple only has potential energy:  E₀ = mgh, where m is the mass of the apple, g is the gravitational acceleration, and h is the height above the ground from which the apple is dropped. When it hits the ground, this energy has converted to kinetic energy: E_f = mv²/2, where v is the velocity we need to find. Equating the two expressions and re-arranging to solve for speed, gives v = (2gh)^1/2.  (Answer: v = 6.26 ms^-1)