Physics Module 5 - Projectile Motion

What assumptions do you make in HSC projectile motion questions?

• Air resistance is negligible, therefore acceleration in the x direction is 0.

• There is a constant vertical acceleration of -9.8m/s squared

What is the equation for resolving initial velocity into vectors?

Ux = Ux x cos(angle)

Uy = Uy x sin(angle)

How do you approach questions involving initial velocity?

• Always draw a diagram

• Resolve into vectors

• Use trigonometry to work out the desired variable.

What is the equation for resolving velocity during flight into vectors?

• Vx = Ux + Ax x t

• Vy = Uy + Ay x t

How do you approach questions involving velocity during flight?

• Always draw a diagram

• Resolve into vectors

• Use trigonometry to calculate the desired variable

What are the equations for resolving the position of a projectile into vectors?

• Sx = initial horizontal position + Uxt + 1/2Axt squared

• Sy = initial vertical position + Uyt + 1/2Ayt squared

How do you calculate the maximum height of a projectile?

• Vy = Uy + Ayt

• Set Vy = 0

• OR - h = -Uy squared/2g

How do you calculate the time taken to reach maximum height?

t = -Uy/g

How do you calculate the time of flight?

• If the projectile is launched and lands in the same Y-position

• t = -2Uy/g

• If the projectile lands in a different Y-position

• s = ut + 1/2at squared

How do you calculate horizontal range?

Xrange = Uxt

How do you calculate launch height?

• If launched from ground level, launch height = 0

• If launched from 5m, launch height = 5m