Vertical throws

With a projectile, after the initial force which is used to set the object in motion, the only force of significance acting on the projectile is the force due to gravity.For example:A ball is dropped from a height of 5m.Calculate the speed at which it hits the ground.Calculate the time it takes to hit the ground.There is no horizontal motion so vertically you can use the constant acceleration formula s = ut + ½at² since acceleration is constant and is equal to +g the acceleration due to gravity.Taking downwards as positive, u = 0 and a = g = 9.81 m s^-2, so 5 = ½ × 9.81 × t², giving t = 1.01 s.Then v = u + at = 9.81 × 1.01 = 9.9 m s^-1.For an object thrown upwards, take upwards as positive: u is positive, a = -g, and v = 0 at the maximum height.