Projectile Motion: The most common type of 2-dimensional kinematics problem is the projectile motion problem. A projectile is any massive object travelling through the air without any forces acting upon it other than gravity. In reality air resistance can be a significant factor, however as a first approximation we will assume that air resistance is negligible; that is we will assume that the effects of air resistance are small enough that we can ignore them. What all of this boils down to is: A projectile has a constant acceleration of g=9.80 m s 2 down. We will solve a projectile problem like every other 2-dimensional vector problem. Break the problem into components. List the known quantities in each direction. A neat labelled diagram will help. In any projectile motion problem, we start the problem knowing: a x =0 m s 2 and a y =−9.80 m s 2 ^ y Because a x =0 m s 2 , v x is constant and there is only one simple equation in the x-direction: d x = v x t If you know any 2 of these 3 variables you can solve for the third. The y-direction is a standard 1-dimensional problem with a constant acceleration: a y =−9.80 m s 2 ^ y Just make a list of the 5 variables: a y , d y , v y , v 0 y and t If you know any 3 of these you can find the rest using the 4 key formulas of kinematics. It is important to rmember that time is scalar. This means that time is always the same for both the ^ x and ^ ydirections! In most projectile problems you will use one direction to find time, then use that time to finish solving the other direction.