Projectile Motion Problems How to solve problems… Contents

Contents Standard Problem Types Skills to know Typical Errors

Standard Problem Types Level ground projectiles Down off of a cliff Up onto a cliff Maximum height Time to a specified vertical displacement Final velocity Contents

Skills to Know Resolve components into orthogonal (perpendicular) components Trigonometric functions Algebra (better…is BETTER; work on it) Calculator error (learn to use FEWER key strokes (less brackets, “EE” button for exponents, etc.) VIFDAT Contents

Level Ground Projectile Final vertical component of velocity is equal but opposite to the initial vertical component; this includes the ANGLE from the horizontal. Contents

Down Off a Cliff Find vertical final velocity component with VIFDAT (d is ‘-’) (vf2 = vi2 + 2ad) Find time of flight using VIFDAT (vf = vi + at) Use average velocity equation to find the Range (horizontal “d”) d = vavgt Contents

Maximum Height Vertical component of velocity is zero at top of trajectory Set vertical vf = 0 Solve for d Contents

Time of Flight Determine the displacement from question Determine if question asks for “on the way up”, “on the way down”, or BOTH Solve for time using VIFDAT and information in question Contents

Final Velocity Determine vertical vf Determine constant horizontal component of v Use Pythagoras to find the hypotenuse of the final velocity vector Contents

Up Onto a Cliff Find vertical final velocity component with VIFDAT (d is ‘+’) (vf2 = vi2 + 2ad) Find time of flight using VIFDAT (vf = vi + at) Use average velocity equation to find the Range (horizontal “d”) d = vavgt Contents

All Projectiles Horizontal component of velocity is constant; projectile does not accelerate in the horizontal direction. Final velocity (the whole vector…not a component) is equal in magnitude, and at the same angle to the horizontal as the initial velocity (just below the horizontal, not above). Contents

Typical Errors Remember: “vf” is NOT the same as “vertical vf” Confusion of trig functions used to find horizontal and vertical components of the initial velocity Vectors in opposite directions NOT given opposite sign (velocity, acceleration, displacement) Algebra Calculator errors Contents