Ch 9 motion
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Ch. 9 Motion. Describing Motion Motion Speed & Velocity Acceleration. Newton’s First Law. Newton’s First Law of Motion An object at rest will remain at rest and an object in motion will continue moving at a constant velocity unless acted upon by a net force. motion. constant velocity.

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Ch. 9 Motion

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Ch 9 motion

Ch. 9Motion

Describing Motion

Motion

Speed & Velocity

Acceleration


Newton s first law

Newton’s First Law

  • Newton’s First Law of Motion

    • An object at rest will remain at rest and an object in motion will continue moving at a constant velocity unless acted upon by a net force.

motion

constant velocity

net force


A motion

A. Motion

  • Problem:

    • Is your desk moving?

  • We need a reference point...

    • nonmoving point from which motion is measured


A motion1

Reference point

Motion

A. Motion

  • Motion

    • Change in position in relation to a reference point.


A motion2

A. Motion

Problem:

  • You are a passenger in a car stopped at a stop sign. Out of the corner of your eye, you notice a tree on the side of the road begin to move forward.

  • You have mistakenly set yourself as the reference point.


B speed velocity

d

v

t

B. Speed & Velocity

  • Speed

    • rate of motion

    • distance traveled per unit time


B speed velocity1

B. Speed & Velocity

  • Instantaneous Speed

    • speed at a given instant

  • Average Speed


B speed velocity2

B. Speed & Velocity

  • Problem:

    • A storm is 10 km away and is moving at a speed of 60 km/h. Should you be worried?

  • It depends on the storm’s direction!


B speed velocity3

B. Speed & Velocity

  • Velocity

    • speed in a given direction

    • can change even when the speed is constant!


C acceleration

vf - vi

t

a

C. Acceleration

  • Acceleration

    • the rate of change of velocity

    • change in speed or direction

a: acceleration

vf: final velocity

vi: initial velocity

t: time


C acceleration1

C. Acceleration

  • Positive acceleration

    • “speeding up”

  • Negative acceleration

    • “slowing down”


D calculations

d

t

v

D. Calculations

  • Your neighbor skates at a speed of 4 m/s. You can skate 100 m in 20 s. Who skates faster?

GIVEN:

d = 100 m

t = 20 s

v = ?

WORK:

v = d ÷ t

v = (100 m) ÷ (20 s)

v = 5 m/s

You skate faster!


D calculations1

d

t

v

D. Calculations

  • Sound travels 330 m/s. If a lightning bolt strikes the ground 1 km away from you, how long will it take for you to hear it?

GIVEN:

v = 330 m/s

d = 1km = 1000m

t = ?

WORK:

t = d ÷ v

t = (1000 m) ÷ (330 m/s)

t = 3.03 s


D calculations2

vf - vi

t

a

D. Calculations

  • A roller coaster starts down a hill at 10 m/s. Three seconds later, its speed is 32 m/s. What is the roller coaster’s acceleration?

GIVEN:

vi = 10 m/s

t = 3 s

vf = 32 m/s

a = ?

WORK:

a = (vf- vi) ÷ t

a = (32m/s - 10m/s) ÷ (3s)

a = 22 m/s ÷ 3 s

a= 7.3 m/s2


D calculations3

vf - vi

t

a

D. Calculations

  • How long will it take a car traveling 30 m/s to come to a stop if its acceleration is -3 m/s2?

GIVEN:

t = ?

vi = 30 m/s

vf = 0 m/s

a = -3 m/s2

WORK:

t = (vf- vi) ÷ a

t = (0m/s-30m/s)÷(-3m/s2)

t = -30 m/s ÷ -3m/s2

t = 10 s


E graphing motion

Distance-Time Graph

A

B

E. Graphing Motion

  • slope =

  • steeper slope =

  • straight line =

  • flat line =

speed

faster speed

constant speed

no motion


E graphing motion1

Distance-Time Graph

A

B

E. Graphing Motion

  • Who started out faster?

    • A (steeper slope)

  • Who had a constant speed?

    • A

  • Describe B from 10-20 min.

    • B stopped moving

  • Find their average speeds.

    • A = (2400m) ÷ (30min) A = 80 m/min

    • B = (1200m) ÷ (30min) B = 40 m/min


E graphing motion2

Distance-Time Graph

E. Graphing Motion

  • Acceleration is indicated by a curve on a Distance-Time graph.

  • Changing slope = changing velocity


E graphing motion3

Speed-Time Graph

E. Graphing Motion

  • slope =

  • straight line =

  • flat line =

acceleration

  • +ve = speeds up

  • -ve = slows down

constant accel.

no accel. (constant velocity)


E graphing motion4

Speed-Time Graph

E. Graphing Motion

Specify the time period when the object was...

  • slowing down

    • 5 to 10 seconds

  • speeding up

    • 0 to 3 seconds

  • moving at a constant speed

    • 3 to 5 seconds

  • not moving

    • 0 & 10 seconds


Vector

VECTOR:

  • Vectors measure using arrows to show direction and magnitude.

  • Shows direction of the object's motion.

    • Ex: velocity, acceleration, force. (all involve a direction)


Can you build the perfect paper airplane

Can you build the perfect paper airplane?

  • Principles:

  • A glider moves through the air without the help of a motor or engine.

  • A glider can move through the air and descend gradually when it is well designed and built.

  • Think about aerodynamics to build a glider that will fly well. "Drag" "Thrust" "Lift" "Gravity“

  • Facts:

  • The design of your glider's body and wings has a lot to do with how well it will sail in the air.

  • Adding some weight to parts of your glider will help it stay up in the air, have lift, and travel in a straight path instead of spinning or nosediving.


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