Date post: | 01-Nov-2014 |
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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