MotionMotion

Speed, acceleration, Speed, acceleration, momentummomentum

Frames of ReferenceFrames of Reference

Object or point from which motion is Object or point from which motion is determineddetermined

Most common is the Most common is the

EarthEarth Motion is a changeMotion is a change

in in positionposition relativerelative to to

a frame of referencea frame of reference

What is motion?What is motion?

If you are standing in one place, and your If you are standing in one place, and your friend walks by you, are you moving friend walks by you, are you moving relative to your friend?relative to your friend? Is your friend moving relative to you?Is your friend moving relative to you? Is either of you moving relative to the Is either of you moving relative to the

earth?earth?

Answer:Answer:

You are moving relative to your friend, You are moving relative to your friend, and your friend is moving relative to you!and your friend is moving relative to you!

You are not moving relative to the earth, You are not moving relative to the earth, but your friend is. You are both moving but your friend is. You are both moving relative to the sun!relative to the sun!

What is motion?What is motion?

If you and your friend are walking down the hall If you and your friend are walking down the hall together at the same speed, in the same direction, together at the same speed, in the same direction, are you moving relative to your friend?are you moving relative to your friend? Is your friend moving relative Is your friend moving relative

to you?to you? Are either of you moving Are either of you moving

relative to the Earth?relative to the Earth?

Answer:Answer: You are NOT moving relative to You are NOT moving relative to

your friend, and your friend is NOT your friend, and your friend is NOT moving relative to you. You both moving relative to you. You both are moving relative to the earth.are moving relative to the earth.

SpeedSpeed

Speed = Distance ÷ TimeSpeed = Distance ÷ Time

D_ D_

S TS T

Example: A car travels 300km in 6 Example: A car travels 300km in 6 hours. What is the speed of the car?hours. What is the speed of the car?

Answer:Answer:

Speed = distance ÷ timeSpeed = distance ÷ time Speed = 300km ÷ 6 hoursSpeed = 300km ÷ 6 hours Speed = 50km/hrSpeed = 50km/hr

More practiceMore practice

1. How far can a plane travel if it flies 1. How far can a plane travel if it flies 800km/hr for 9 hours?800km/hr for 9 hours?

2. How long does it take a ship to go 500 2. How long does it take a ship to go 500 km if it travels at a speed of 50km/hr?km if it travels at a speed of 50km/hr?

AnswerAnswer

1. 1. DD SS T T

DD800800 9 9

800km 800km ▪ 9hrs = 7200km ▪ 9hrs = 7200km hrhr

AnswerAnswer

2. 2. DD SS T T 500 500 5050 T T

500km ÷ 500km ÷ 50km50km = 10 hrs = 10 hrs hrhr

VelocityVelocity

Speed in a given direction.Speed in a given direction.

What is the velocity of a boat that What is the velocity of a boat that travels from St. Peter to Mankato travels from St. Peter to Mankato (10 miles) in 15 minutes?(10 miles) in 15 minutes?

AnswerAnswer

Speed = distance ÷ timeSpeed = distance ÷ time Speed = 10 miles ÷ 15 Speed = 10 miles ÷ 15

minutesminutes Speed = 0.67 mi/minSpeed = 0.67 mi/min Velocity = 0.67 mi/min SouthVelocity = 0.67 mi/min South

Change your answer to Change your answer to mi/hr!mi/hr!

0.67mi/min x 60min/hr = 0.67mi/min x 60min/hr =

40 mi/hr40 mi/hr

Distance-time graphsDistance-time graphs

On your paper, graph the following:On your paper, graph the following: D (m)D (m) T (sec) T (sec)

00 00 55 77 1010 14 14 1515 21 21

Was your graph a straight Was your graph a straight line?line?

A A distance-time graphdistance-time graph which is which is a a straight linestraight line indicates indicates constant speedconstant speed..

In constant speed, the object In constant speed, the object does not speed up or slow does not speed up or slow down. The acceleration is zero.down. The acceleration is zero.

Graph the following on a Graph the following on a distance-time graph:distance-time graph:

D (m)D (m) T (s)T (s) 00 00 55 11 2020 224545 338080 44125125 55

0 1 2 3 4 5

Was your graph a curve?Was your graph a curve?

A graph that A graph that curvescurves on a on a distance-time graphdistance-time graph shows shows that the object is that the object is acceleratingaccelerating

Distance-time graphsDistance-time graphs

Describe the motion of the object as Describe the motion of the object as shown in the shown in the

graph.graph.

From 0-8 sec, constant speed:(25 m/sec);From 8-12 sec, no motion;From 12-16 sec, acceleration;From 16-20 sec, constant speed

Speed-time graphsSpeed-time graphs

Using the distance-time graph from Using the distance-time graph from the last frame, draw a speed time the last frame, draw a speed time graph. First fill in the table below:graph. First fill in the table below:

Average Speed (m/s)Average Speed (m/s) Time (sec) Time (sec)

________ 0 to 80 to 8

________ 8 to 128 to 12

________ 12 to 2012 to 20

25

0

37.5

What does your graph look What does your graph look like?like?

Constant speedConstant speed will be a will be a horizontal horizontal line on a speed time line on a speed time graph. graph.

If the speed If the speed decreasesdecreases, the line , the line will slant will slant downdown..

If the speed If the speed increasesincreases, the line , the line will slant will slant upup..

What do the following speed-What do the following speed-time graphs depict?time graphs depict?