Vectors and Motion in Two Dimensions
Two-dimensional motion looks like a new topic and is really just one-dimensional motion run twice in parallel. Pick perpendicular axes, split the velocity into one component along each, then handle each axis with the tools from Topic 1.2. The two axes share only one variable: time. Whatever happens vertically never touches the horizontal motion, and the reverse.
Almost every wrong answer on this topic is a leak between axes. Students treat horizontal motion as if it slows the fall, treat the peak of the arc as a moment when the ball is at rest, or grab the wrong trig function for a component without first checking which axis the angle was measured from. Each one dissolves the moment the two axes are written on separate lines.
The work
3 ways in · any order
Lesson
Vectors and Motion in Two Dimensions
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In 2D, the two axes are independent and time is the only thing they share. The lesson decomposes vectors into perpendicular components and walks projectile motion as horizontal and vertical solved separately on the same clock, then closes with a ten-scenario applet that drills component independence, the vector-representation traps, and the at-the-peak misread where students confuse $v_y = 0$ with $a = 0$.
Diagnostic
10-item topic check
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Ten items mapped to the 2D failure modes: coupled-components reasoning (treating x and y as if they affect each other), vector-representation traps with arrows in two directions, the scalar/vector category error in 2D, and the at-the-peak trap where $v_y = 0$ is mistaken for $a = 0$.
Targeted Practice
Drill a single misconception
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Pick one of the failure modes you've missed and grind it on its own. The round is adaptive: two correct in a row clears the misconception and you move on.