Welcome to Class

What are some ways that objects move?

Agenda

• Speed challenge• Speed and Velocity Notes

Welcome to Class

How can you tell when something is moving?

Agenda

• Speed and Velocity Notes

MotionDef. – an objects change in position relative to a

reference point

• To observe motion you need a reference point/frame of reference– Observe an object in relation to a stationary object

• Describe direction of an object with a reference direction– North, south, east, west, up, down

Q: What was our frame of reference for Speed Challenge?

Motion• Distance measures the path taken

• Displacement – change in position of an object– Must be a straight line (shorter than distance)– Must be in a particular direction

Q. Which should you use when calculating how much gas you will use on a trip?

Q. Which does the saying, “As the crow flies” refer to?

Speed and Velocity

• An object is moving if it changes position against some background that stays the same

• Speed – how fast an object moves– Distance and time– m/s– Equal distance in equal amounts of time =

constant speed

Constant Speed

Average Speed

• Distance traveled divided by the total time

Speed = distance/time v=d/t

If you run 100 m in 10 seconds what is your average speed?

Velocity

• Velocity is speed and direction– 2.0 m/s north– 500 m/s toward California

• Direction can be positive or negative-4 -3 -2 -1 0 1 2 3 4

Calculating

If a person runs 30 meters in 10 seconds. What is their speed?

If a car travels at 150 km/h. How long would it take them to travel 350 km?

If you travel 120 km north in 3 hours, what is your velocity?

Welcome to Class

If you travel 120 km north in 3 hours, what is your velocity?

Agenda

• Finish Speed Notes• Speed Lab• Speed Problems

A little bit more about Velocity

If you are on a bus going 15 m/s east then you are traveling 15 m/s east.

While it is moving you stand up and walk down the bus’s aisle while it is moving.

Q: Are you still moving the same velocity as the bus?

15 m/s east

1 m/s east

15 m/s east + 1 m/s east = 16 m/s east

1 m/s west

15 m/s east

15 m/s east + (- 1 m/s west) = 14 m/s east

Welcome to Class

What is the difference between speed and velocity?

Agenda

• Practice Problems• Quiz• Speed and Velocity problems

What is the speed of a cyclist that travels 60 km in 2 hours?

Agenda1.Review Speed2.Acceleration

Outside tomorrow!

Calculating Speed

1. A boat is traveling at a speed of 36 km per hour. It has to travel a distance of 210 km. How long will it take?

2. A car takes four hours to reach its destination. The distance was 340 miles. What was its speed?

3. A car travels 300 km in six hours. What is the speed of the car?

4. What is the speed of a jet plane that flies 7200 km in 9 hours?

5. The speed of a cruise ship is 50 km/hr. How far will it travel in 14 hours?

6. The speed of a rocket is 16,000 km/hr, and it will take 66 hours to complete its mission. How far will it go?

Acceleration

• We know when our speed increases or decreases our velocity changes– Also when we change direction

• When you change velocity you are accelerating– Change in velocity is called acceleration– Acceleration includes direction as well– Units: m/s2

Acceleration as change in direction• Acceleration is a change in the direction

– WHY?

• Acceleration is a change in velocity– Velocity is speed AND direction

• If you are traveling at a constant speed and are turning in a circle, are you accelerating?

Calculating Acceleration

• Measure velocity at different times

Equation: acceleration = final velocity – initial velocity

timeOr

a = ∆v/t

Calculating Acceleration

• If acceleration is small, velocity is changing slowly• If acceleration is large, velocity is changing rapidly

• Positive acceleration means object is speeding up• Negative acceleration means object is slowing

down– Velocity is decreasing

Examples

A skier was originally going at 20 m/s and stopped in .5 s. What is the skier’s acceleration?

A flowerpot falls off a second story windowsill. The flowerpot starts from rest and hits the sidewalk 1.5 s later with a velocity of 14.7 m/s. What was the acceleration of the flowerpot?

More examples

You accelerate your skateboard along a straight path from 0 m/s to 4.0 m/s in 2.5 s. What is your average acceleration?

Find the average acceleration of a northbound subway train that slows down from 12 m/s to 9.6 m/s in .8 s.

What does ∆ stand for?

Agenda1.Review Acceleration2.Outside – lab

Acceleration• Speeding up or slowing down

– a = ∆v/t

• If a person travels at 10 m/s and then speeds up to 15 m/s in 1.5 s, what is their acceleration?

• A person starts at 20 m/s and accelerates at 2 m/s2 until they reach 40 m/s. How long did they accelerate?

A person on a sled slides down a hill at 5 m/s until they are stopped. It takes them 5 s to

stop. What is their acceleration?

Agenda1.Finish Acceleration Lab

a. Graphing

2.Acceleration Problems

Quiz Tomorrow!

What is acceleration?

Agenda1.Quiz2.Finish Graphing3.Acceleration Problems

1. What is this a graph of?2. What is happening in this graph?

Agenda1.Finish Graphing

1. Talk about graphs

2.Motion Graphs

Calculate the speed from 12 s to 18 s

Agenda• Go over motion graphs worksheets• Acceleration Problems

Calculating Acceleration

A car accelerates from a standstill to 60 m/s in 10 s. What is the acceleration?

A cyclist accelerates from 5 m/s to 10 m/s in 5 s. What is the acceleration?

A runner accelerates from 2 m/s to 6 m/s at a rate of 2 m/s2 . How long did it take?

A runner achieves a speed of 11 m/s after he starts. It took him 9 s to reach that speed. How long did it take? What distance did he cover?

A car is going 45 m/s and slows down to 24 m/s. It takes the car 5 s to slow down. What was the cars acceleration?

After a car accelerates at 5 m/s2 for 3 seconds it’s speed is 50 m/s. What was the initial velocity?

A person on a sled starts at the top of the hill standing still. They go down the hill and reach an acceleration of 3 m/s2 . It took 5 seconds to get to the bottom of the hill. What was the final velocity at the bottom of the hill?

A person on a sled starts at the top of the hill standing still. They go down the hill and reach an

acceleration of 3 m/s2 . It took 5 seconds to get to the bottom of the hill. What was their change in velocity?

Agenda for Monday Oct. 25th 1.Review Acceleration Problems (due)2.SQ3R Laws of Motion