What's the difference between vector and trajectory in Physics?

Question

So from what I understand the Trajectory is the entire motion a particle makes from the initial location in the universe to the final location in time.

Velocity from what I understand is simply the the speed and direction of movement through space a particle is heading.  It's usually used in relation to the time.

But what is a vector then?  It sounds to me like vector is the same as the trajectory.

Steve4Physics · Answer

Velocity is an *example* of a vector (a quantity with size and direction).

A trajectory is just the path followed by a projectile.

If you have point P on a trajectory, you can tell the direction of the projectile when it passes through point P. The (instantaneous) direction is along the tangent at P.

But you can't tell how fast the projectile is going when it passes through point P just from the trajectory.  The velocity includes the speed information as well as the direction. The trajectory contains no speed information.

Robert J · Answer

A vector is simply speed and direction, at the instant of measurement or whenever it applies.

Trajectory is an entire path, as in the trajectory of a cannon shell or a thrown ball - a curve with changing speeds, as it's pulled down by gravity and slowed by air drag.

The vector continuously changes during the flight of the object.

alex · Answer

r(t) =<x(t),y(t),z(t)> is the position , at time t, of the particle in space

What's the difference between vector and trajectory in Physics?

3 Answers