Motion and free fall

Motion in ONE Dimension 1

Motion - a change in position

Frame of reference - a point against which a position is measured

displacement

  • Change in position

  • final position - initial position

  • Can be positive (right / up) or negative (left / down)

Average Velocity

  • displacement divided by the time interval

  • change in position/change in time (m/s)

Average Speed

  • It does not include direction, while velocity does

  • does not include direction, while velocity does

  • distance travel/time travel (m/s)

Graphing Motion

slope = rise/run

In distance-time graph, slope = speed/velocity

Motion in ONE Dimension 2

Acceleration

  • change in velocity/change in time (m/s²)

Vi

a

+

+

Moving right as it speeds up

+

-

Moving right as it slows down

-

-

Moving left as it speeds up

-

+

Moving left as it slows down


Graphing Motion

In velocity-time graph: slope = acceleration

area = displacement/distance

Free Fall

  • Assumes no air resistance

  • Acceleration is constant for the entire fall

  • Acceleration due to gravity (a or g)

  • Has a value of -9.81 m/s² (or -10 m/s²)

  • Negative for downward

Velocity

Acceleration

explanation

Halfway up (V>0)

+

-

move up, constantly slow down

At the peak (V=0)

zero

-

stop and change direction

Halfway down (V<0)

-

-

move down, constantly speed up


Equation

Vavg = Δx/Δt

aavg = Δv/Δt，Vf = Vi + aΔt

Vavg = (Vi + Vf)/2

Δx = Vi Δt + ½ a Δt²

Vf² = Vi² + 2aΔx