How do I add a shot tracer on a golf ball

As long as the object you're tracking is very clear and defined you can.

Intro to object tracking in Final Cut Pro for Mac - Apple Support

If you don't mind creating the trace manually, AND you have Motion, it's not all that difficult.

You need Motion to publish the Stroke Filter (Filters > Border > Stroke) - just add it to the Effect Source and publish **every parameter**.

In Final Cut, add a Custom generator (Solids Category) over your footage. Set the Color to 0.5, 0.5, 0.5 (medium gray) and the Compositing > Blend Mode to Overlay (you'll hardly know it's there.)

Add a Draw Mask to the generator. Set your playhead to the beginning of the trace and set a control point. Move the playhead to the *peak* of the trace (it'll always be some kind of arc), then move the playhead to the *point of contact* where the direction of the object will change... from there you can move the playhead to various points in the motion and set control points.

When the path is traced, you will need to "complete" the Draw Mask, so set points significantly *away* from the path points and finish the "shape" some kind of way.

If you added the Stroke effect, it should appear — otherwise, add it here. You can fine tune the shape of the trace with the stroke line in place. **Important** - in the Stroke effect, CHECK: Hide Source — this will get rid of any appearance of the generator and leave only the Draw Mask lines — then reset the Blend Mode to Normal.

From there, you can animate (keyframe) a mask over your tracer line.

If you think you could put up with this method... get back with me — I have a "Tracer Mask" effect. You'll have to manually keyframe its position over time, but it has the ability to set a fade over time as well as set the Opacity of it's "parts" over their lifetime (gradual fades by time). It's really quite easy and doesn't take as long as it sounds.

(Sorry about the *tiny* GIFS... we're only allowed 2MB max...)