I keep getting “Independent horizontal and vertical motion” questions wrong in Motion in a Plane. What's the trap?
using the resultant speed as the horizontal speed throughout the flight.
The usual trap: using the resultant speed as the horizontal speed throughout the flight. How to avoid it: one clock, two equations: solve x and y separately, then recombine. Go back to the definition — Gravity changes only the vertical velocity of a projectile. Horizontally, velocity stays constant when air resistance is ignored. The two motions share the same clock but otherwise evolve independently.
Key point
Independent horizontal and vertical motion
Common mistake
using the resultant speed as the horizontal speed throughout the flight.
Memory tip
one clock, two equations: solve x and y separately, then recombine.
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