8.1 Motion

8.1 Motion

Pages 252-258

Goal 1

Understand the relationship between speed, distance, and

time; also solve speed equations.

• Speed– Distance traveled in a certain amount of time

• Constant speed– Distance covered per unit time remains the

same

• Speed Graph– Y-axis distance– X-axis time– Faster Steeper slope– Slower flatter slope

• Speed equation (aka velocity equation)– Remember your units!

Speed = distance

time

v = d

t

• Example– Remember your units!

– Find Ms. Acker’s speed if she traveled 10 meters in 20 seconds on her skateboard.

d =

t =

v =

• Speed equation (aka velocity equation)– To find distance– Remember your units!

Distance = speed x time

d = v x t

• Example– Remember your units!

– How far did the ping pong ball travel if it rolled across the table at a speed of 2 meters per second for 0.5 seconds?

d =

v =

t =

• Speed equation (aka velocity equation)– To find time– Remember your units

time = distance

speed

t = d

v

• Example…– Remember your units!

– How long will it take for a bowling ball to travel 10 meters if it is rolling at a speed of 7 meters per second?

t =

d =

v =

Goal 2

Distinguish between speed and velocity

• Speed is distance per time

• Velocity is distance per time in a direction

Velocity or Speed?

A lion ran at 12 m/s.

Velocity or Speed?

A lion ran at 12 m/s towards the gate.

Velocity or Speed?

A science 9 student walked 4 miles/hour.

Velocity or Speed?

A science 9 student walked 4 miles/hour towards the ala carte line.

Goal 3

Understand momentum and use the momentum equation.

• Momentum– An object’s mass times it’s velocity

• Momentum equation– Remember your units!

Momentum = mass x velocity

p = m x v

• Example…– Remember your units

– What is the momentum of a 13 g swallow* traveling with a velocity of 10 m/s to Europe?

*unladen African Swallow

• Momentum equation– Find mass– Remember your units!

Mass = momentum

velocity

m = p

v

• Example…– Remember your units

– What is the mass of a train with a momentum of 300 g*m/s traveling at a velocity of 10 m/s towards the front door?

• Momentum equation– Find velocity– Remember your units!

velocity = momentum

mass

v = p

m

• Example…– Find velocity– Remember your units

– What is the velocity of a baseball traveling with a momentum of 290 g*m/s if it has a mass of 145 g?

• Practice problems

– Page 255: # 1, 3

– Page 257: #1a, 1c, 1e

– Page 258: # 7-9