Allow varying mass in all screens?

[samreid]

@patricialoeblein suggested:

1. I think that it is important for students to be able to see how mass and thermal energy are related, so I would ask you to consider adding back varying mass to all scenes. One reason for this is that the added feature of "not stick to track" provides complexity with thermal energy. I believe students may need to investigate in a more rich context how mass effects thermal energy because of friction considering that falling onto the track causes friction.

[ariel-phet]

@samreid and @patricialoeblein I see no reason why we could not add a varying mass to the track playground, which would achieve @patricialoeblein goal. The reason on the first two screens to keep varying mass and friction separate is to allow students to explore these ideas independently at first, which we believed to be important scaffolding in the design of the basics version. However, since the playground is meant to be open-ended, it seems appropriate to allow control of all variables there.

[samreid]

So @patricialoeblein recommends to add Mass controls to "Friction" and "Playground", and @ariel-phet recommends to add Mass controls just to "Playground"?

Adding it to "Playground" sounds good to me, I think it should be omitted from "Friction" screen to keep it simpler.

[patricialoeblein]

I think adding it back to the playground is good. I am not sure if that will be enough.

I am still concerned about how students will reconcile the changes in thermal energy due to the friction and the "landing on track" and the cement friction (I think it always has the same as the track, so hopefully that will be simple). I personally think being able to change the mass might help, but maybe they will test dropping the skater from different heights to figure out that the potential energy only varies by height and that is partially converted to thermal energy in the track collision. If the team thinks that is one of the goals and that is best achieved by leaving out varying mass, I can see the point of leaving the feature out..

Perhaps this comment belongs some where else: The version of the google doc https://docs.google.com/document/d/1WfDUrnVlZvIwFYiyfVh8IBm8k61bZKMu-KG_FlTxgOk/edit that I am seeing does not define the goals in terms of scenes. As the team will be writing a Tips, a more clear scene to goal correlation would strengthen the doc and enable a more clear Tips doc.

[samreid]

I added "Mass" slider to playground screen. I also moved Trish's comment to the Google Doc. This feature will be ready for review in the next dev version.

[samreid]

Fixed in http://www.colorado.edu/physics/phet/dev/html/energy-skate-park-basics/1.0.0-rc.3/energy-skate-park-basics_en.html and reassigned to @patricialoeblein for testing.

[patricialoeblein]

It just so happens that my group of NGSS PhET teachers are writing a lesson for this sim. It has been brought up that it seems odd that Mass variability is not on the Friction scene since Force of Friction is directly related to normal force (which varies with mass). Even the MS teachers are wondering why they should have to go to the Playground to get to this important idea. If someone from the design team wants to talk with the teachers group, we meet Mondays and Thursdays for 2 more weeks 9-1:30 on the 10th floor of Jila.

[patricialoeblein]

I am beginning to think that it would be more important to have Mass on the Friction Scene and move the Stick/unStick feature to the Playground only. Then teachers can use the Friction scene to address the standard that mass effects the amount of thermal energy in both important ways 1. mass is related to friction force which causes thermal energy and 2. PE can be converted to Thermal energy by just dropping the Skater from the sky. I put this comment the mass issue ticket 148, 147, and 146 also because I do not know where it should go.

[samreid]

In the above commit, I made this change:

Show mass slider on all screens, and only show attach/detach radio buttons on the playground screen

I published it here for review, let me know what you think: http://www.colorado.edu/physics/phet/dev/html/energy-skate-park-basics/1.0.0-rc.4/energy-skate-park-basics_en.html

[samreid]

We reviewed this at last Thursday's meeting, and it seem good to go. Closing.

[ariel-phet]

I think there is some confusion about this issue. The skater in this simulation is rolling...rolling involves only the force of static friction, and static friction does no work. So the "Friction" control we have is really related to frictional forces within the system (like friction in the bearings of the wheels, air resistance, etc...) which is not affected by normal force, so I am not exactly understanding how we are addressing normal force affecting friction here??

[patricialoeblein]

The teachers working on the NGSS standard involving Energy think that the Skater friction is approximating sliding friction. They are used to the old sim which would allow students to make a qualitative connection between thermal energy and friction. If the team decides to drop the connection because it is rolling friction then a sim page with Teaching tips needs to be made soon. This is a very popular sim and if we change the features too much, I believe more teachers will use the Java version because they have lessons that already align with those features. That's just my 2 cents.

[ariel-phet]

Hey @patricialoeblein....I don't think anybody is advocating for dropping that connection. This sim is most definitely advocating for the qualitative connection between thermal energy and friction. In fact, I believe that was the rationale in the Java version of Energy skate park basics to only having the Friction slider available on the friction tab. That way the sim in the configuration was specifically focused on the the thermal energy goal, and the mass was not conflated. I liked your idea that both the mass and friction are adjustable in the playground, but one of the reasons the basics version was designed the way it was, was to scaffold exploration. First see that mass affected potential energy, but not the conservation of energy. Then see the role of friction and thermal energy. So we would be matching the Java version of Energy Skate Park basics on the first two screens (which had many successful interviews).

[patricialoeblein]

I understand that the interviews show students get to the playground tab and can possible make the required relationship between mass, friction, and thermal energy. The concern teachers have is that they have to write more in the student directions to get them to see the relationship. I wanted to share the common concern from the teachers writing lessons that align with NGSS and PhET guides. They felt like not having mass on the Friction tab made it more difficult for them to have the students make the connections with few directions. As I have mentioned, I was not on the design team, but I was asked to make a ticket so that we could discuss the teachers point of view.

[ariel-phet]

Fair enough. Let's leave as is with the Mass slider included on the Friction screen.