MOTION

Chapter 11

Measuring Motion

Motion of an object must be observed within a frame of reference.

Frame of reference – describes the motion of an object relative to fixed points.

What is the fixed point in the photograph?

Distance and displacement

Distance measures how far or the length of the motion.

Displacement not only measures how far but in what direction.

• 50 MILES

50 MILES WEST

• DISPLACEMENT MUST DESCRIBE WHERE THE OBJECT IS MOVING.

• (NORTH, SOUTH, EAST, WEST, UP, DOWN, TOWARD SPRINGFIELD ETC.)

Speed and Velocity

Speed describes how fast an object moves.Speed = distance What does this mean?

time

The units for speed are (m/s, km/h, mi/h etc)

Velocity describes how fast and in what direction.

Don’t forget to include the direction. This

dog has a velocity of 10 mi/h to the east! Golly, he’s

fast. Or is he?

Let’s work some problems, shall we.

Write the equation for speed.

S = DT

Could we rewrite this so we don’t have a fraction?

YES HOW?Get rid of the T by multiplying both sides by T

and there you have it! S x T = D x T T

ST = D

Okay, now for some practice

A twizzler is 16 cm in length and you can eat the entire twizzler in 45 seconds. What is your twizzler eating speed?

Equation D = ST or S = D/THere we go… Plug in your numbers to the

appropriate spot.D = 16 cm X = 16 cmT = 45 sec 45 secS = X X =

Motion video

video

Distance vs. time graph

You can determine the speed, distance and time of an object by reading a distance vs time graph.

1 2 30

10

20

30

40

50

60

70 Distance vs. time

doghorsemouse

Time (s)

Distance(m)