A ball is thrown vertically upwards into the air. It rises a vertical distance of 3.1 m before falling to the ground. Assuming that all of the ball's initial kinetic energy is converted into gravitational potential energy as the ball rises, at what speed was the ball thrown into the air?
You should assume g = 9.8 m s-2 and give your answer to an appropriate number of significant figures and in the correct SI units.