11/6 (p 62) Motion Notes- Speed

• IQ: What is motion? How is it different from speed?

Reference Point: A place or object used to compare and determine if an object is in motion. Should not be moving, should be visible to compare. http://rpdp.net/terms/mid/full/m/motion.htm

What would be the best reference point to tell if the canoe is moving or not?a.The waterb.The skyc. The shored.The lighthousee.The island

• Earth rotates on its axis at 1,100 mph or 1670 km/hr.

• Earth orbits the Sun at 68,000 mph or 107,000 km/hr

• The whole galaxy rotates at 490,000 mph

Measuring Distance

Meter – international unit for measuring distance.

= 50 m1 mm

Speed is the distance traveled by a moving object over a period of time.

Formula: Speed = Distance(m) Time(s)

Calculating Speed• Speed (S) = distance traveled (d) / the

amount of time it took (t).

• Copy on left page:

S (speed, how fast, rate)= d/t SI unit m/sD (distance, how far)= s x t SI unit mT (time, how long) = d/s SI unit s

D

S T

Calculating speed

• If I travel 100 kilometer in one hour then I have a speed of…

• 100 km/h• If I travel 1 meter in 1 second then I have a

speed of….• 1 m/s• If I travel 100 km in 2 hours, I have a

speed of 100 km/2 h= ____

S = d/t

Speed =distance

time

A snail crawls 1 m in 100 seconds.What is the speed of the snail?

= 1 m

Problem 1 (left hand side p.): Create a problem like the one above and solve to find the speed. Please use different numbers!

= .01 m/s100s

Problem 2 =I ran for 2 hours at a speed of 6 km/h. How far did I run?

Types of Speed

• Constant speed = unchanging speed over a certain period of time.

• Speed is usually NOT CONSTANT– Ex. Cars stop and go regularly– Runners go slower uphill than downhill

• Average speed = total distance traveled/total time.

• Instantaneous speed= speed at any given time.

Problem 3: Tina ran 1000 m in 3 minutes. Then ran another 1000 m uphill in 7 minutes. a. Did she have a constant speed? b. Find her average speed.• A) 100 m/min• B) 2000 m/min• C) 10 m/min• D) 200 m/min • E) 20 m/min

Total Dist. = 1000 m + 1000 m = 2000 m

Total Time = 3 min + 7 min = 10 min

Ave speed = total dist/total time =

2000m/10 min = 200 m/min

Problem 4

Jane ran 10 km in 2 hours, and the next 5 km in 1 hour.

Did she have a constant speed? (Find speed for each part of her run, is it the same?).

What is her average speed? (Total d/total t)

OQ: How long would it take a car driving at 100 km/h to go 600 km?

11/6 Motion Notes: Velocity

IQ:

Did the football in the cartoon move? Did the kid move? How can you tell?

It has bothspeed and direction. Ex.50km/h south, 10m/s NE

Do all these planes have the same speed?

Istheirvelocitydifferent?

Problem : Rocket 1 goes 2000 km in 2 hrs. towards the East. Rocket 2 goes 3600 km in 3 hrs. towards the East. Do they have the same

a. Speed?

b. Velocity? Explain.

Which of the following could be the velocity of a moving object?

A. 12 m/s

B. 100 m NE

C. 0.5 m/s W

D. 1300 s N

11/7 Speed Challenge labIQ: Word bank: Constant speed, velocity, average speed, instantaneous speed

a. I hiked up the mountain at a speed of 1 m/s- _____________

b. At t=10s the rocket was going1000 m/s-________________

c. The plane flew at 700 km/h E-__________

d. The earth rotates at 1100 mph.-___________.

11/12 Motion Notes: Acceleration

IQ: Complete #1, 3, and 4 on white half sheet.

Acceleration• Acceleration is a change in

speed or direction of an object.

• Accel = final vel.-initial vel. m/s2

Time m/s2

Calculating Acceleration

• If an object is moving in a straight line

Time

SpeedInitialspeedFinalonAccelerati

__

Units of acceleration:m/s2

Calculating Acceleration

0 s 1 s 2 s 3 s 4 s

0 m/s 4 m/s 8 m/s 12 m/s 16 m/s

2/4

4

/0/16

__

sm

s

smsmTime

SpeedInitialSpeedFinalonAccelerati

A cheetah goes from 0 to 60 mi/h in 3s. What is its acceleration?

Types of acceleration

• Increasing speed, positive accel.– Example: Car speeds up at green light

• Decreasing speed, negative accel./deceleration

– Example: Car slows down and comes to a stop at red light

• Changing Direction– Example: Car takes turn (can be at constant

speed)

screeeeech

Centripetal acceleration

Is the car below accelerating?

Physics of NFL

• A car that starts from rest and speeds up to 30 km/hr in 10 seconds has positive acceleration.

On your left page calculate the acceleration of the car above.

• A car that slows down, and comes to a stop from going 100 km/hr in 5 secs. has a negative acceleration or deceleration.

• On your left hand side page, calculate the acc. of the car above.

Question

• How can a car be accelerating if its speed is a constant 65 km/h?

• If it is changing directions it is accelerating

OQ: Which of the following is NOT accelerating?a. The earthb. A skier going downhillc. A car sitting in the drivewayd. A school bus stopping.

Centripetal Acceleration• When you move in a circular motion,

you have continuous acceleration (always changing direction)

• Acceleration from spinning• Centripetal means “toward the

center”

OQ: Draw the v/t graph for an object that starts out at a high velocity, slows down constantly and comes to a stop.