Practice physics class test — Year 3: universal gravitation.
15 questions drawn at random from a bank of 25, on the block of the programme your teacher is finishing: every attempt is a different test. No penalty for wrong answers, so answer even if you are not sure. At the end you receive by email the correct answer to every question and your weak topics — with an account you see them straight away here on the page. The step-by-step solution unlocks with your first lesson.
A class test is the written test an Italian high-school class sits after each block of the programme; this practice version is multiple choice.
Note on school types. At the liceo scientifico gravitation closes the Year 3 mechanics; where physics starts in Year 3 the block slips to Year 4, after work and energy.
Test in ItalianThe questions of this simulator are in Italian, as in the real exam.
Programme covered by the test
- Kepler’s three laws and the law of areas
- The law of universal gravitation and the constant G
- Gravitational field of a planet and the value of g
- Orbital speed and period of a satellite
- Geostationary satellites and apparent weightlessness
- Gravitational potential energy with zero at infinity
- Escape velocity
Two worked examples from the test
Le tre leggi di Keplero descrivono il moto dei pianeti attorno al Sole.
Secondo la prima legge, qual è la forma dell'orbita di un pianeta e dove si trova il Sole?
Solution
La prima legge di Keplero afferma che ogni pianeta percorre un'ellisse e che il Sole occupa uno dei due fuochi dell'ellisse.
Il secondo fuoco resta vuoto: non c'è nulla di fisico in quel punto.
L'orbita circolare non è sbagliata come approssimazione (le orbite dei pianeti sono ellissi poco schiacciate), ma la legge parla di ellisse; e in un'ellisse il centro non coincide con un fuoco.
Conseguenza importante: la distanza pianeta-Sole cambia durante l'anno, e si passa dal punto più vicino (perielio) al più lontano (afelio).
Un asteroide percorre attorno al Sole un'orbita di semiasse maggiore . La Terra ha e periodo anno.
Usando la terza legge di Keplero nella forma quanto vale il periodo di rivoluzione dell'asteroide?
Solution
Scrivo il rapporto con i dati della Terra, che valgono in queste unità:
Quindi
Attenzione ai due errori tipici: anni significa aver usato (proporzionalità diretta, che qui non vale), mentre anni viene dall'aver fatto la radice del semiasse invece che del suo cubo.
Le unità sono coerenti perché tempi e distanze compaiono come rapporti con i valori terrestri: anni con anni, UA con UA.
In the online practice test you will find 13 more questions like these; the correct answer to every question arrives by email.
Prefer paper? Download the test as a PDF (15 questions, 4 pages · 84 KB, ready to print). You receive the solutions by email after taking it online.
Download the PDFWhat a physics test on gravitation looks like
Kepler’s three laws applied to a planet or a satellite, the law of gravitation with the calculation of g on another celestial body, orbital speed and period, the geostationary orbit and often the escape velocity.
The mistake that costs the grade
Using the height above the surface instead of the distance from the centre of the planet: the formulas use r measured from the centre, so radius plus height. And confusing apparent weightlessness in orbit with the absence of gravity: gravity is there, and it is exactly the centripetal force.
How to use this practice test
Take it once cold, without revising and with the timer on: it is there to show you where you stand, not to look good. Then look at your weak topics, revise only those — usually two or three, not the whole chapter — and retake it after a few days. The 15 questions are drawn from a bank of 25, so the second attempt is not the same test and the scores are genuinely comparable.
Is the score not enough?
See which topics lost you the most marks, then read the first physics test of Year 3 — or we look at your results together: the diagnostic is free.