IV. Motion Equations for Problem Solving


When an object is moving at a constant acceleration we can use the following equations to find motion information
A. Equations (on the Reference Table)

 

1. Average Velocity: V = (Vi + Vf)/2

 

2. Acceleration: a = (Vf - Vi)/t

Cross multiply & Solve    Vf = Vi + at

 

3. Displacement: V = Δd/Δt

B. Other equations on reference table are derived from 3 equations above

Take Equation 3 and solve for d

Δd = V Δt

• Substitute Equation 1 into previous equation

Δd =[(Vi + Vf)/2]Δt 

 

Since Vf = Vi + at

 

Δd =[(Vi + (Vi + at)/2]Δt 

 

Gather like terms and solve for d
 

Δd =Vit +1/2at2