The Apex Is Not a Pause
Film a toss in slow motion against a door edge and step through it one frame at a time. Along the floor the ball covers the same distance every frame, straight through the top; up the edge the steps shrink to nothing and then reverse. Only the vertical component ever reaches zero, so the ball is never actually at rest — except at 90°.
Cara memakai simulasi ini
- Press Roll the film and then step frame by frame with the arrow buttons
- Press Jump to the highest point and read the velocity components there
- Raise the frame rate to 240 fps to resolve the top of the arc finely
- Set the launch angle to 90° to find the one case that really does pause
Yang perlu diamati
- Horizontal frame-to-frame spacing is identical everywhere, including across the apex
- Vertical spacing shrinks to nothing at the top and then grows again downwards
- The speed at the apex equals the horizontal component, which is never zero for a slanted launch
- Acceleration is g at the apex just as it is at launch and at landing
- Only a vertical throw brings the ball to a genuine momentary stop
Fisika di baliknya
At the highest point vᵧ = 0, which is exactly what defines the apex, but vₓ = v₀ cos θ is untouched because no horizontal force acts anywhere in the flight. The speed there is therefore v₀ cos θ, not zero, and the velocity vector is horizontal rather than absent. The acceleration is g throughout, including at the apex, so the ball is changing velocity at the top just as fast as anywhere else. Only a vertical launch, where cos θ = 0, leaves nothing behind and brings the ball genuinely to rest for an instant.