Final answer:
A projectile fired straight upward will have a speed of 0 m/s at the top of its trajectory, which is also true for one fired at an angle concerning its vertical component.
Step-by-step explanation:
The question is about projectile motion, a concept in physics. When a projectile is fired straight upward, its speed at the top of its trajectory will be 0 m/s, because at the peak of its path, the projectile momentarily stops before starting to fall back down due to gravity. If the projectile is fired upward at an angle, such as 18° from the horizontal, only the vertical component of the initial velocity will affect how fast it is moving at the top of its trajectory. At the top, the vertical velocity component will be 0 m/s, similar to the straight upward shot, because gravity will have decelerated the projectile to a momentary halt in the vertical direction, while the horizontal component of the velocity remains unchanged (assuming no air resistance).