Final answer:
When an arrow is projected vertically up with a velocity of 40 m/s and reaches a target in 3 s, the velocity of the arrow at that point will be determined by the force of gravity as it falls back down.
Step-by-step explanation:
When an arrow is projected vertically up with a velocity of 40 m/s, it will eventually reach a maximum height before coming back down to the ground. This is because of the force of gravity acting on the arrow. Since the arrow reaches a target in 3 s, we can determine its velocity at that point.
At its highest point, the velocity of the arrow will be 0 m/s. This is because the arrow momentarily comes to a stop before falling back down. So, the initial upward velocity of 40 m/s will decrease to 0 m/s at the highest point, and then increase again as it falls back down due to gravity.
Therefore, the velocity of the arrow when it reaches the target will be determined by the force of gravity acting on it as it falls back down. The velocity will be negative to indicate the downward direction.