Physics Chp 2

Displacement – is the difference between the intitial position and the final position. It does not matter how far you really went.

ex. Flying to Boston via Sea or Salt Lake or Houston.

All 3 you have the same displacement and it is symbolized as Δx.

Needs a value and direction with units

Velocity is the change in x divided by timev = Δx/ Δt Avg. velocity is just comparing any two points of

data. Instantaneous velocity is at one instant in time

and is the tangent to the graph of Δx vs Δt

Slope of tangent to the graph gives the velocity at that instant in time.

Acceleration a = Δv/ Δt graphical const vs variable

Equations when a = constant

vf = vo +aΔt

Δx = 1/2(vo + vf)Δt

Δx = voΔt + 1/2a(Δt)2

vf

2 = vo2 + 2aΔx

• Ex Find the final velocity if you toss a ball from your car traveling North at 200 m/s and your arm accelerates it 50 m/s2 N for 0.3 s.

• Vo = 200 m/s N a = 50 m/s2 N t = 0.3 s

• vf = vo +aΔt

• vf = 200 m/s + 50 m/s2(0.3s)

• Vf =

Free Fall is just when a = -9.81 m/s2 Ex If it takes 13 s for a rock dropped off a cliff to

hit the bottom, how high is the cliff? Ignore the echo issue.

• vo = 0 m/s a = -9.81 m/s2 t = 13s

• Δx = voΔt + 1/2a(Δt)2

• Δx = 0m/s(13s) + ½(-9.81m/s2)(13s)2

• Δx = -830m cliff is really 830m Why

• Ex How fast did the rock hit the bottom of the cliff?

• vo = 0 a = -9.81 m/s2 t = 13s ∆x = -830m

• vf2 = vo

2 + 2aΔx

• vf2 = 02 + 2(-9.81 m/s2)(-830m)

• vf2 =

• vf = ?????