Free fall and the equivalence principle revisited
Pendrill, Ann Marie LU
(2017)
In Physics Education
52(6).
- Abstract
Free fall is commonly discussed as an example of the equivalence principle, in the context of a homogeneous gravitational field, which is a reasonable approximation for small test masses falling moderate distances. Newton's law of gravity provides a generalisation to larger distances, and also brings in an inhomogeneity in the gravitational field. In addition, Newton's third law of action and reaction causes the Earth to accelerate towards the falling object, bringing in a mass dependence in the time required for an object to reach ground - in spite of the equivalence between inertial and gravitational mass. These aspects are rarely discussed in textbooks when the motion of everyday objects are discussed. Although these effects are... (More)
Free fall is commonly discussed as an example of the equivalence principle, in the context of a homogeneous gravitational field, which is a reasonable approximation for small test masses falling moderate distances. Newton's law of gravity provides a generalisation to larger distances, and also brings in an inhomogeneity in the gravitational field. In addition, Newton's third law of action and reaction causes the Earth to accelerate towards the falling object, bringing in a mass dependence in the time required for an object to reach ground - in spite of the equivalence between inertial and gravitational mass. These aspects are rarely discussed in textbooks when the motion of everyday objects are discussed. Although these effects are extremely small, it may still be important for teachers to make assumptions and approximations explicit, to be aware of small corrections, and also to be prepared to estimate their size. Even if the corrections are not part of regular teaching, some students may reflect on them, and their questions deserve to be taken seriously.
(Less)
- author
- Pendrill, Ann Marie
LU
- organization
- publishing date
- 2017-11-01
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Physics Education
- volume
- 52
- issue
- 6
- article number
- 065002
- publisher
- IOP Publishing
- external identifiers
-
- scopus:85032223161
- ISSN
- 0031-9120
- DOI
- 10.1088/1361-6552/aa5e38
- language
- English
- LU publication?
- yes
- id
- ed4efdff-9ffa-4628-8cfd-feea6e4dfe55
- date added to LUP
- 2017-11-07 12:39:58
- date last changed
- 2022-04-25 03:46:48
@article{ed4efdff-9ffa-4628-8cfd-feea6e4dfe55,
abstract = {{<p>Free fall is commonly discussed as an example of the equivalence principle, in the context of a homogeneous gravitational field, which is a reasonable approximation for small test masses falling moderate distances. Newton's law of gravity provides a generalisation to larger distances, and also brings in an inhomogeneity in the gravitational field. In addition, Newton's third law of action and reaction causes the Earth to accelerate towards the falling object, bringing in a mass dependence in the time required for an object to reach ground - in spite of the equivalence between inertial and gravitational mass. These aspects are rarely discussed in textbooks when the motion of everyday objects are discussed. Although these effects are extremely small, it may still be important for teachers to make assumptions and approximations explicit, to be aware of small corrections, and also to be prepared to estimate their size. Even if the corrections are not part of regular teaching, some students may reflect on them, and their questions deserve to be taken seriously.</p>}},
author = {{Pendrill, Ann Marie}},
issn = {{0031-9120}},
language = {{eng}},
month = {{11}},
number = {{6}},
publisher = {{IOP Publishing}},
series = {{Physics Education}},
title = {{Free fall and the equivalence principle revisited}},
url = {{http://dx.doi.org/10.1088/1361-6552/aa5e38}},
doi = {{10.1088/1361-6552/aa5e38}},
volume = {{52}},
year = {{2017}},
}