welcome to class what are some ways that objects move?
TRANSCRIPT
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