Gravity on a RollGravity on a Roll

Gravity Rules!Gravity Rules!

AndAnd

Gravity Gravity AlwaysAlways Wins Wins

What will happen …What will happen …

if you drop this heavy book if you drop this heavy book and a sheet of paper from the and a sheet of paper from the

same height?same height?

Engage

What would Aristotle say?What would Aristotle say?What would Galileo say?What would Galileo say?

What do you say?What do you say?

Marble/Steely RaceMarble/Steely RaceMaterials: Materials:

track (two yard sticks taped to form a track (two yard sticks taped to form a groove)groove)

marblemarble

steelysteely

stopwatchstopwatch

metric tapemetric tape

graph papergraph paper

calculatorcalculator

Explore

Marble/Steely RaceMarble/Steely Race

Reading a ruler and Reading a ruler and stopwatch.stopwatch.

Explore

Marble/Steely Ball Race I:Marble/Steely Ball Race I:a closer look?a closer look?

Procedure Outline:Procedure Outline:

1)1) Construct and set up track.Construct and set up track.

2)2) Assign jobs (teams of 4).Assign jobs (teams of 4).

3)3) Measure and record ball mass.Measure and record ball mass.

4)4) Predict the relation between the times Predict the relation between the times for two balls of different mass to for two balls of different mass to travel the same distance (a little less travel the same distance (a little less than a meter).than a meter).

5)5) Measure and record for each ball.Measure and record for each ball.

Explore

Marble/Steely Ball Race: Marble/Steely Ball Race: DiscussionDiscussion

Explain

1.1. Compare data – any pattern?Compare data – any pattern?

2.2. What is the problem?What is the problem?

Precision - Reaction timePrecision - Reaction time

3.3. How can we fix this?How can we fix this?

More trials – AverageMore trials – Average

4.4. Aristotle vs. Galileo.Aristotle vs. Galileo.

Newton’s Second Law of Newton’s Second Law of MotionMotion

► Any force acting on an object will Any force acting on an object will change its motion.change its motion.

Explain

► How much change there is How much change there is depends on the object’s mass and depends on the object’s mass and applied force.applied force.

Speed, Velocity, AccelerationSpeed, Velocity, AccelerationSpeed:Speed:

Explain

how fast something is going; average speed is measured by the distance traveled divided by the time needed to travel that distance

Velocity:Velocity: the speed and direction something is moving

Acceleration:Acceleration: any change in motion of an object; a change in direction and/or speed

Marble/Steely Ball Race II:Marble/Steely Ball Race II:a closer look?a closer look?

Procedure Outline:Procedure Outline:

1)1) Predict the motion: Sketch a position Predict the motion: Sketch a position vs.vs. time graph like you did for the trip to time graph like you did for the trip to Grandma’s house. Grandma’s house.

2)2) Measure and record the position at every Measure and record the position at every second.second.

3)3) Plot position Plot position vs.vs. time. time.

4)4) Calculate the average speed for each time Calculate the average speed for each time interval (distance traveled / time taken – interval (distance traveled / time taken – recall facet 40).recall facet 40).

5)5) Plot average speed vs. time – pattern?Plot average speed vs. time – pattern?

Explore

Newton’s Second Law of Newton’s Second Law of MotionMotion

► Any force acting on an object will Any force acting on an object will change its motion.change its motion.

Explain

► How much change there is How much change there is depends on the object’s mass and depends on the object’s mass and applied force.applied force.

Take better measurements.Take better measurements.

Extend

How could you take better How could you take better measurements?measurements?

Washers on string Washers on string

Try a second mass in experiment Try a second mass in experiment II.II.

Evaluate

1.1. Apply the terms speed, Apply the terms speed, velocity, and acceleration to velocity, and acceleration to what you observed.what you observed.

2.2. Revisit the introductory Revisit the introductory demonstration and apply the demonstration and apply the terms speed, velocity, and terms speed, velocity, and acceleration to what you acceleration to what you observed.observed.

Homework Due 1/23/07 in Homework Due 1/23/07 in classclass

1.1. H1: Replot your two sets of data on one sheet H1: Replot your two sets of data on one sheet of graph paper. The top plot should be of graph paper. The top plot should be position vs. time and the bottom plot should position vs. time and the bottom plot should be velocity vs. time. Choose good scales that be velocity vs. time. Choose good scales that show the data clearly.show the data clearly.

2.2. On the other side of the graph paper describe On the other side of the graph paper describe what is happening in each graph using the what is happening in each graph using the terms on the other side of this sheet.terms on the other side of this sheet.

Remember to do the Diagnoser Set by 6 PM Remember to do the Diagnoser Set by 6 PM Monday (1/22/07). See the class web page.Monday (1/22/07). See the class web page.