EVERYTHING IS MOVING!!!

Halloween Edition

Linear Motion

Motion is Relative – there is no place in the universe that isn’t moving, so we must state motion “relative” to something else.

Linear Motion Reference Frame – the spot designated “not

moving”… all motion is described relative to it (usually the ground).

Sometimes we will assign other places as reference frames. This changes the relative motion of ALL other objects.

SpeedA measure of distance covered in a time

period, or how fast it is moving.

S= d/t

distance

Ex. A car moves 60km in 3 hrs, it has a speed of20km/hr

Speed

distance

S= d/t

Which has a > speed? Why?Same distance < time

Speed: TypesInstantaneous Speed – how fast an

object is moving at an “instant” of time.Ex: Speedometer

Average Speed = total distance/ total time

Speed vs. velocity

V , velocity is a measure of distance covered in a time period, or how fast it is moving with a direction.

V = d/tEx. A witch that moves 60km North in 12 hrs has a velocity of: 5km/hr North

Constant vs Changing Velocity

Acceleration Δ Velocity

Δ time

Objects accelerate anytime their speed or direction changes.

How many accelerators in the car???

Δ (delta) means “change”

Gravity!Acceleration due to gravity (g) on Earth is about 10 m/s/s

REGARDLESS OF WEIGHT!!!What falls faster, a bowling ball or pebble?

Free Fall How Fast? How Far?

Time (s) Speed (m/s) Distance (m)

0 0 01 10 52 20 203 30 454 40 805 50 125

Equationt 10t ½ 10t2

Bluh, Bluh, Bluh, I Vant To Suck Your

Bluuuud!

v = d/t

Velocity

d = vtt = d/vvdt

a = Δv/Δt

Acceleration

Δv = aΔt Δt= Δv/aaΔv

Δt

d = ½ at2

Distance (free fall)

a = 2d/t2 t= √(d/½ a)

½ ad

t2

Equations (pg 1) When velocity is constant:

V =d/t d=Vt t=d/V When the object is accelerating:

a =ΔV/Δt ΔV =a Δt t= ΔV/ad=1/2at2

Remember, gravity is an acceleration and can be substituted for a in any of the equations when gravity is doing the accelerating.

Distance Time Graphs

Constant Velocity Graphed

Distance Time Graphs #2

Acceleration Graphed

Ideal Models and Air Resistance

Many examples will apply only in the “Ideal World” where air resistance/ friction doesn’t exist.

-10

m/s

2

+10

m/s

2

Speed & acceleration =

Zero!

40m/s

2 s

30m/s

-10m/s/s

-10m/s/s

1 s

20m/s

0 s

-10m/s/s

3 s 10m/s-10m/s/s

4 s 0m/s

-40m/s

6 s

-30m/s

+10m/s/s

+10m/s/s

7 s

-20m/s

8 s

+10m/s/s

5 s -10m/s+10m/s/s

4 s 0m/s

Baseball ends up in his hand!

0

60

30 90

120