Final answer:
In projectile motion with negligible air resistance and an initial angle between 0° and 90°, the velocity of a projectile is never zero until it lands, the minimum velocity occurs at the apex of the trajectory, and although the projectile will never have the same velocity vector as the initial one, except at t = 0, the speed can be the same at launch and upon landing at the same elevation.
Step-by-step explanation:
Projectile Motion and Velocity
When discussing projectile motion on level ground with negligible air resistance and with the initial angle not being 0° or 90°, several questions arise about velocity and acceleration. For question (a), the velocity of a projectile is not zero at any point in the trajectory until the object lands - it always has some horizontal component of velocity. At the highest point in its trajectory, however, the vertical component of velocity is zero.
Regarding question (b), the velocity is a minimum at the apex of the projectile's path. This is because, at this highest point, the vertical component of the velocity is zero, although there is still a horizontal component. Conversely, the velocity is a maximum at launch and just before impact, assuming that the launch and impact occur at the same elevation.
For question (c), the velocity of the projectile cannot be the same as the initial velocity at any other time, except at t = 0, because velocity is a vector and its direction changes throughout the motion. However, the speed, which is the magnitude of the velocity vector, can be the same as the initial speed at two moments: at launch and when the projectile lands, assuming it lands at the same elevation from which it was launched.