Metodologie per la didattica
della fisica
Irene Marzoli
irene.marzoli@unicam.it
Portale Docenti
Nuffield Science Teaching Project
• Sviluppato da insegnanti in Gran Bretagna
dal 1962
• Insegnamento di chimica, fisica e biologia
nella scuola secondaria (O-level
examination)
• Guida per l’insegnante e non un semplice
sillabo
• 5 volumi + uno dedicato ad esami e test
Teaching science for understanding
• Physics for all
• Sperimentare in autonomia (a scientist for
a day)
• Apprezzare l’unitarietà della fisica
(connected knowledge)
• Capire il significato di formule ed
equazioni
• Discutere le possibili soluzioni – imparare
a porre domande
Examining for understanding
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Cheap recall vs. simple recall
Expensive recall
Intelligent guessing
Teaching recall
Open or loose questions
Esami e verifiche
a) State an expression for the distance, s,
travelled from rest in time t by an object
moving with constant acceleration a.
b) How far will an electric light bulb fall from
rest in 10 seconds?
Esami e verifiche
a. In the expression s = ut + 1/2 at2,
(i) What does u stand for?
(ii) What does ut tell us?
(iii) Explain why the 1/2 is there.
b. If you used this expression for the free fall of an electric
light bulb dropped from rest, you could expect it to
predict quite well the distance fallen in 1 or 2 seconds.
But if you used the expression for a 10-second fall, the
prediction would disagree seriously with a test by
experiment. Suggest why.
c. What kind of motion would you expect for the bulb after
10 or 20 seconds of fall? Why?
Controllare l’ordine di
grandezza
Quesito 1
Quant’è, approssimativamente, la capienza
di un cucchiaio da minestra?
a) 1.2 x 10-3 m3
b) 120 mL
c) 12 x 10-3 L
d) 1.2 cm3
e) 0.12 x 10-3 dm3
Soluzione quesito 1
Quant’è, approssimativamente, la capienza di un
cucchiaio da minestra?
a) 1.2 x 10-3 m3 = 1.2 L
b) 120 mL
c) 12 x 10-3 L = 12 mL
d) 1.2 cm3 = 1.2 x 10-3 dm3 = 1.2 mL
e) 0.12 x 10-3 dm3 = 0.12 mL
Una scodella di minestra 240 ml, 20 cucchiaiate,
circa 12 mL.
Fermi problem
From a letter written by Prof. Philip Morrison of Cornell University
“... It is by no means possible to specify the training and
readiness of a prospective graduate student by a mere
list of topics. There is a kind of power over the theoretical
and experimental studies in which he has engaged
which is difficult to define, but whose presence is
perhaps more important than much knowledge which is
more formal and complete. There is one test for such
power which is at the same time a remarkably apt
method for its development. That is the estimation of
rough but quantitative answers to unexpected questions
about many aspects of the natural world. The method
was the common and frequently amusing practice of
Enrico Fermi, perhaps the most widely creative physicist
of our times. …”
Fermi problem
• Back-of-the-envelope
calculation
• Stima dell’ordine di
grandezza
“How many pencils would it take
to draw a straight line along the
entire Prime Meridian of the earth?”
University of Maryland Fermi problems site
www.physics.umd.edu/perg/fermi/fermi.htm
Quesito 2
Quanto pesa un metro cubo di aria?
a) 1.21 g
b) 121 g
c) 12.1 kg
d) 1.21 kg
e) 12.1 g
Soluzione quesito 2
Quanto pesa un metro cubo di aria?
Composizione: 4/5 N2 + 1/5 O2
N14, O16
1 mole di aria: (4 X 28 + 32)/5 g = 28.8 g
Una mole occupa un volume di 22.414 L
−3
28.8 ×10 kg
-3
ρ≈
≈ 1.28 kg m
-3
3
22.414 ×10 m
Force Concept Inventory
• Il “buon senso” e l’esperienza quotidiana
sono incompatibili con la meccanica
Newtoniana
• I metodi didattici tradizionali non
scalfiscono questi preconcetti
• Il risultato è indipendente dall’insegnante e
dal programma
• Cercare di capire come gli studenti
ragionano ed imparano