In physics what is momentum

Momentum and momentum set

Curriculum reference

 

Middle school5
Realschule curriculum plus(I)7/10
(II + III)8/10
high schoolcurrent curriculum7
CurriculumPlus8/10

Video

Download 154 MB (right click)

Download 4.6 MB (right mouse click)

If the video is shown in daylight with the help of a projector, the brightness and contrast should be set in the projector menu so that the measured values ​​can be seen in the video.

Notes on implementation

When setting up the experiment, the video shows small green paper tubes around the thread and red spots of glue on the thread. They do not actually serve the purpose of the experiment, but are only intended to make the thin thread recognizable. They were therefore omitted when the experiment was repeated.
Attaching the threads is quite a nuisance; For the lesson, it is a good idea to prepare a number of threads in advance. You can also cut the thread with sharp scissors.
The experiment was carried out with the Cassy data acquisition system. The measurement files used are available for download here (right mouse click).
The runway must be adjusted reasonably precisely in order to avoid excessive deviations in the measured values. The trolleys may have to be stopped at the end of the taxiway to prevent them from rolling through the light barriers a second time.

Didactic advice

The introduction of the impulse and the formulation of the impulse theorem are often deductive. One starts with Newton's third axiom under the assumption of constant acceleration. By rearranging this equation one then obtains momentum and momentum set, whereby the product of mass and speed is defined as momentum.
If you want to proceed inductively, the above experiment can be used. If the mass of the carriages is varied, the students can see that the product of mass and speed is constant. So one gets the momentum definition and momentum set from the experiment at the same time. Here there is also the possibility of going into the nature of conserved quantities.
With the introduction of the curriculum plus in grade 7, the effect of forces with the relationship F · Δt = m · Δv is to be discussed. The definition of the impulse is essentially on the right-hand side, so that there is a good opportunity to link it to the mechanics of the 7th grade.

Further material and links

Videos


Elastic shock pushing mass larger
Download, 154 MB
Download, 13 MB
Download, 2.8 MB

Elastic shock impacting mass smaller
Download, 150 MB
Download, 13 MB
Download, 2.8 MB

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