Question

A 1 kg mass is projected from the edge of a 20 m tall building with an initial speed of 10 m/s. The kinetic energy (in J) of the mass just before it hit the ground is:

Answer 1

The final kinetic energy is the sum of initial kinetic and potential energies according to the conservation of energy:

$$KE_f=KE_i+PE_i,\\ KE_f=\frac12mv^2+mgh=246\text{ J}.$$