Vectors and Forces
Forces have both magnitude and direction, making them vectors that need special treatment. You'll constantly switch between vector notation ai+bj and finding magnitudes using Pythagoras' theorem.
Speed versus velocity trips up loads of students! Speed is always positive (it's a scalar), whilst velocity can be positive or negative depending on direction. Distance is the magnitude of displacement, and speed is the magnitude of velocity.
Force diagrams are absolutely crucial - always draw them! You'll see normal reactions (perpendicular to surfaces), tension (along strings), friction (opposing motion), weight (always downward), and air resistance (opposing motion through air).
Essential Skill: Master the relationship |V| = √a2+b2 for finding vector magnitudes - you'll use it constantly throughout mechanics!
Converting between different units before calculating is non-negotiable. Metres, seconds, kilograms, and metres per second squared are your standard SI units. Most exam disasters happen because someone forgot to convert!