Projectile Motion

Simplify projectiles into Horizontal Motion (x) and Vertical Motion (y)

Only 3 Variables in X-direction. Speed = Distance/time

Only time is common to both X and Y directional motion. Velocity, displacement, and acceleration are different. eg: velocity in y direction is different to speed in X direction.

Equation: Speed=distance/time

No acceleration. Therefore Initial speed=final speed

Usually start with X direction to find time.

Define Positive (+) direction. Anything that acts downwards (eg acceleration, displacement) = -

List out all known and unknown variables (U, V, a, t, S)

Substitute into correct SUVAT (Constant acceleration) Equation.

At highest point, V=0. a is always known and is = -9.8 if upwards is the defined positive direction.

Is the Vector sum of Horizontal and Vertical Velocities

Use Pythagoras theorem

Can be used to find the speed of the projectile at any location.

Final Speed = Sqrt [(Vx)^2+ (Vy)^2]

Use Usin(angle) and Ucos(angle) to break an initial U into the X and Y directions

Draw a triangle and use the deifinition of sin and cos to work out components of the initial velocity vector

The adjacent side always gets the cos(angle)

A projectile can have only an initial horizontal velocity and zero vertical velocity

When an object is released, its initial velocity will be the velocity of the object that is releasing it (eg package dropped from a plane, or from a spinning wheel).

If the object is finally moving downards, V must be negative (provided up is the positive direction)

If the final position is below the initial position, S is negative (provided up is the positive direction). Objects always move from initial position to final position and the direction of S can be found by drawing an arrow starting from initial position.