THURSDAY, DEC. 11 TH p. 106, 107

THURSDAY, DEC. 11 TH /11/14 Thurs. L.T.: I can write a 3 part hypothesis and a procedure to investigate the average speed of rolling objects. DO NOW: Al and Zane both need to travel 1 mile to get to school. Both arrive at school in 15 mins. but traveled at different average speeds. How could this be? ……………… Reflection Qs: What is the difference between constant speed and average speed? Use something from class to back up your answer. 107 Title: Need for Speed 2 Q: How do the avg. speeds of various rolling objects compare over the course of 1 meter? Hypothesis: If… then… because… Procedure: includes 3 variables and numbered, logical steps Speed Rankings:

5 TH PERIOD  Variables:  RV: time (so that we can calculate speed: speed = d/t)  MV: different rolling objects of dif. Masses  CV: track (1 m), ramp height and length, release point at top of ramp with no added force,

4 TH PERIOD  Variables:  CV: positioning of the ramp, “release” of ball – no added force, same release point (top of ramp), length of track (1 m), how we gather data (start timer at beginning of meter; stop at end of 1 m)  MV: mass of rolling object  RV: time (so that we can calculate speed S = d/t)

3 RD PERIOD  Variables:  CV: ramp angle (3 books tall, purple line on book edge), ball needs to roll to the end of 1 meter, length of track (1m), surface of track (tabletops), “release” of rolling object  MV: mass of rolling object  RV: time, so that we can calculate speed (meters/sec)

5 TH PERIOD HYPOTHESIS  If you increase the mass of the rolling object,  Then its speed after rolling down a ramp will (1) increase? 2) Decrease? 3) Stay the same?)  Because…  1) normal force and gravity creates more acceleration.  2) bigger mass has more sliding friction, so slower speed.  3) the friction and elevation is the same

HYPOTHESIS  If the rolling object has more mass,  Then its speed after rolling down a ramp will be greater,  Because:  - the combined normal force and gravitational pull will make a bigger force downhill on a larger mass than a smaller mass  - a larger mass will have more force to overcome sliding friction

3 RD PERIOD  Hypothesis:  If we roll round objects of different mass,  Then the more massive ones will move with (less) speed,  Because the object with more mass needs more force to overcome friction.  Because the bigger the mass the less acceleration of the object.  Because the more mass the ball has the less speed it will go compared to a smaller (massed) ball.

 Mass of rolling objects:  Basketball:  Volleyball  Softball:  Baseball:  Ping pong ball:  Steel marble:

FINISH FOR HW  Procedure:  CV:  MV:  RV:  1. Gather materials.  2. Set up ramp with science books: 3 on bottom, 1 on top. Line up top book’s purple stripe to the spines of the stacked pile.  3.