To determine the velocity at which the ball strikes the ground, we need to consider the motion of the ball in two stages: the upward motion and the downward motion.
Upward motion: The initial velocity of the ball is 5 m/s, and it is thrown vertically upward. Due to the force of gravity acting against its motion, the ball's velocity decreases until it reaches its highest point. At the highest point, the ball momentarily comes to rest before starting its downward motion. At this point, the velocity is 0 m/s.
Downward motion: During the downward motion, the ball accelerates due to the force of gravity. The acceleration due to gravity is approximately 9.8 m/s² (neglecting air resistance). The downward motion is symmetric to the upward motion, meaning the velocity will change by the same magnitude but in the opposite direction.
Since the velocity is initially 0 m/s at the highest point, the ball will have the same magnitude of velocity (but in the opposite direction) when it strikes the ground. Therefore, the velocity at which the ball strikes the ground will be 5 m/s, but in the downward direction.
Note: This analysis assumes there are no other external factors affecting the ball's motion, such as air resistance.