Student Conception: Constant speed needs cause

[Matt Anthes-Washburn]

Student Conception: Constant speed needs cause
Students believe constant speed needs some cause to sustain it (Atlas of Science Literacy (2001), American Association for the Advancement of Science, Project 2061. pp.62-63)

Identifiers
In this activity, students roll a ball down a ramp onto an upward sloping ramp.  Students may think the ball rolled down the ramp will go a certain distance along the upward slope and stop. You can have them make predictions about how far the ball will roll on the ramp when it is lowered. Students may predict the ball will go the same distance and stop (without reaching the same height).

Formative Assessment Question
Draw a diagram of the two-ramp system on the board. Have each group mark the point reached on the second ramp on the diagram so the class can see general agreement on how far the ball rolled. When you lower the ramp in FYTD, modify the diagram and label potential end points (A, B, C, etc.) Poll the class for predictions of where the ball will reach before they test it experimentally. Return to the predictions and compare them to experimental results.

Interventions
It is important for students to make predictions to help them to differentiate between acceptable and unacceptable evidence of a phenomenon. Pay attention to the students’ answers to FYTD 6a), where they explain their predictions for where a ball will stop on the uphill ramp.  The key is for students to see that the ball doesn’t need anything special to keep rolling. Each time you extend and lower the ramp, the ball will keep rolling farther and farther. As the students lower the ramp, they should predict where the ball will stop. When the ball rolls significantly farther, students should be surprised by the results and reassess their conceptions of what it takes for the ball to keep rolling. In the end, they need to imagine a smooth flat surface that goes on forever. Will the ball ever stop?

[Scott Bartholomew]

My students always say there is a force of the ball even when it is a free-falling projectile.  I have to remind them to create a FBD and show where the "force" is coming from!  They are usually suprised that they can not identify a cause of the force they think the ball has.

[Amy Stewart]

Mark and I wonder:  do students think that friction can always be ignored?

[Ken Dugan]

My observation is that students really started the activity thinking that to make things move, a force must maintian contact.

[Janie Martin]

This one of my favorite activities, my students really learn alot from this activity.

[Scott Bartholomew]

Mark and I wonder:  do students think that friction can always be ignored?

Yes, it is important to help students decide when they can neglect friction!

[cswartzwelder]

My students always say there is a force of the ball even when it is a free-falling projectile.  I have to remind them to create a FBD and show where the "force" is coming from!  They are usually suprised that they can not identify a cause of the force they think the ball has.

Having students complete a survey before discussing this topic is always an eye-opener!

[Matt Anthes-Washburn]

My students always say there is a force of the ball even when it is a free-falling projectile.  I have to remind them to create a FBD and show where the "force" is coming from!  They are usually suprised that they can not identify a cause of the force they think the ball has.

Having students complete a survey before discussing this topic is always an eye-opener!

Nice