use conservation of energy principles in both questions ...
initial kinetic energy = gravitational potential energy + final kinetic energy1. A stone of mass 0.5 kg is projected vertically upwards with an initial velocity of 4.0ms^-1. What is its kinetic energy when it reaches a height of 0.5m?
1. initial total mechanical energy - work done by friction = final total mechanical energy
2. you can answer this question