RyL61FbBBVpMt

Newton’s third law – mutual interaction between bodies

Source: licencja: CC 0.

Trzecia zasada dynamiki Newtona – wzajemne oddziaływanie ciał

You will learn
  • to experimentally present the third Newton's law and learn about its application,

  • to experimentally demonstrate the validity of the third Newton's law and show its application in practice.

Exercise 1

Answer the questions.

1. What is an interaction?
2. Can you only interact directly with other body?
3. What types of interactions do you know?
4. When do the forces balance?

Watch the slideshow.

R18IihCly02kT1
Pokaz multimedialny - działanie sił akcji i reakcji. Instrukcja obsługi z poziomu klawiatury: 1. Uruchomienie aplikacji - ENTER, 2. Na każdym ze slajdów czytany jest automatycznie tekst alternatywny po polsku, 3. Przy pierwszym uruchomieniu na pierwszym slajdzie, czytanie tekstu po angielsku - TAB, 4. Przejście między slajdami: do następnego slajdu - TAB, do poprzedniego slajdu - TAB + SHIFT, 5. Przejście do czytania napisu po angielsku - strzałka w górę + strzałka w dół (czyta tekst po angielsku widoczny na slajdzie).
Source: GroMar, licencja: CC BY 3.0.
Rgs9RVCho7zUW1
nagranie abstraktu

The following conclusions can be drawn based on the presented slides.

1. Arek attracts Bolek, but at the same time Bolek attracts Arek.
2. The boys act on each other with some force.
3. These forces have the same magnitude, but opposite directiondirectiondirection. These are the forces of actionactionaction and reactionreactionreaction.
4. The forces of action and reaction are not balanced because they are applied to two different bodies.

R1M0n8SFlLsCf1
Source: GroMar, licencja: CC BY 3.0.
Experiment 1
Experiment 1
Hypothesis
R1Z6v0WzBzhVu
nagranie abstraktu

The magnitude of the forces of actionactionaction and reactionreactionreaction are the same.

RWyI4yC1qhNzI
nagranie abstraktu
You will need
  • two carts (two toy cars),

  • two small flat magnets,

  • two dynamometers,

  • plasticine,

  • strong thread or thin string.

Instruction
RgHmLP3wkKaUz
nagranie abstraktu

1. Conduct the experiment on a flat surface, e.g. on a table with a smooth countertop or rails with a suitable spacing.
2. Attach the magnets to the front of the carts with plasticine.
3. The carts facing each other with magnets should attract each other.
4. Attach the thread to the back of each cart.
5. Attach the dynamometers to the ends of both threads.
6. With the help of a friend or a colleague, do not let the carts approach each other, pulling the end of the dynamometers. Make sure that the dynamometers are (if possible) parallel to the table surface.
7. Stop the carts at a short distance from each other.
8. Read the value indicated on the dynamometers.
9. Repeat the experiment several times.

Summary
RqsispnZ6Kzba
nagranie abstraktu

Both dynamometers in our experiment indicated the same values.

The carts attracted each other with the same magnitude of the forceforceforce, but with opposite direction.

These were the forces of action and reaction from magnets (magnetic forces).

Forces were applied to two different magnets, so they could not balance.

Newton's third law
Definition: Newton's third law
R1Up2Rv9vDZNQ
nagranie abstraktu

When the body A acts on the body B with a certain forceforceforce FAB, the body B acts on the body A with the force FBA of the same magnitude, but the opposite directiondirectiondirection.

Wektor siły F z indeksem dolnym AB równa się minus wektor siły F z indeksem dolnym BA.  Wartość siły F z indeksem dolnym AB równa się wartość siły F z indeksem dolnym BA.
Wektor siły F z indeksem dolnym AB równa się minus wektor siły F z indeksem dolnym BA.  Wartość siły F z indeksem dolnym AB równa się wartość siły F z indeksem dolnym BA.
RB0wpe0SaWoLp1
nagranie abstraktu

The third Newton’s lawNewton’s third lawthird Newton’s law is often called action‑reaction lawaction - reaction lawaction‑reaction law.

These forces cannot be balanced because they are applied to two different bodies.

Exercise 2
Ru2EoDLcD4j8Y1
nagranie abstraktu

A man with a mass of 80 kg is standing at the bus stop with a backpack with a mass of 30 kg on his back. What is the force acting on the ground? What is the force the ground is acting on his feet? Give characteristics of these forces.

Exercise 3
R1FoASqdceC3Y1
nagranie abstraktu

Which of the presented pictures correctly shows the force system resulting from mutual interactionsmutual interactionsmutual interactions?

R1W0RSgQNfUvO1
Source: GroMar, licencja: CC BY 3.0.
Exercise 4
R1D0OIl5Y1ppL1
nagranie abstraktu

Using the illustration depicting the construction of a space rocket engine, explain how this type of engines work.

RdA3RFkceGHGk1
Source: GroMar, licencja: CC BY 3.0.
R1TOSS9VMxYjQ1
Source: GroMar, licencja: CC BY 3.0.
Summary
R1QJO3XgDqdon1
nagranie abstraktu
  • There are many types of interactions in nature. The value of force is a measure of the interaction. The interactions are mutual, that is, if we trigger a certain action by applying force, we must expect the reactionreactionreaction of the body on which we act.

  • The fact that the interactions were mutual was noticed by the English scholar Isaac Newton, who lived at the turn of the 17th and 18th centuries. The results of his research in this area are formulated in the form of the third Newton’s lawNewton’s third lawthird Newton’s law.

  • The third Newton's law is that when the body A acts on the body B with a certain force, the body B acts on the body A with the forceforceforce of the same magnitude, but the opposite directiondirectiondirection. These forces cannot be balanced because they are applied to two different bodies.

  • The third Newton's law is also called the action‑reaction lawaction - reaction lawaction‑reaction law. Each actionactionaction is accompanied by a reaction equal in magnitude, but with the opposite direction. However, it should be remembered that the forces do not balance, because they have a different point of application.

Exercises

RG6Sd8qQ9tfdU
Exercise 5
Wersja alternatywna ćwiczenia: The third Newton’s law is fulfilled when the result of interaction of the bodies is Możliwe odpowiedzi: 1. only rest., 2. rest when one body acts on the other force, the same as the value but the opposite. In the third principle, the dynamics are not information about motion., 3. only uniform rectilinear motion or uniformly accelerated motion., 4. only uniform rectilinear motion.
zadanie
Source: GroMar, licencja: CC BY 3.0.
Exercise 6

On the table lies a magnet with a mass of 0,2 kg, and above it an iron bar of the same mass hangs on a dynamometer. What is the force the magnet acts on the table if the dynamometer shows a force of 3 N. Present the force system in the drawing.
Assume g=10ms2.

Exercise 7

Give four examples in English of the occurrence or application of the third Newton’s law.

RPtciT0L0yDvy
Exercise 8
Wersja alternatywna ćwiczenia: Match Polish terms with their English equivalents. punkt przyłożenia Możliwe odpowiedzi: 1. mutual interactions, 2. acting point, 3. balancing of forces, 4. resultant force, 5. Newton’s third law równoważenie sił Możliwe odpowiedzi: 1. mutual interactions, 2. acting point, 3. balancing of forces, 4. resultant force, 5. Newton’s third law oddziaływanie wzajemne Możliwe odpowiedzi: 1. mutual interactions, 2. acting point, 3. balancing of forces, 4. resultant force, 5. Newton’s third law III zasada dynamiki Newtona Możliwe odpowiedzi: 1. mutual interactions, 2. acting point, 3. balancing of forces, 4. resultant force, 5. Newton’s third law siła wypadkowa Możliwe odpowiedzi: 1. mutual interactions, 2. acting point, 3. balancing of forces, 4. resultant force, 5. Newton’s third law
RhEuUQruhGbeH
Interaktywna gra, polegająca na łączeniu wyrazów w pary w ciągu jednej minuty. Czas zaczyna upływać wraz z rozpoczęciem gry. Jeden ruch to odkrywanie najpierw jednej potem drugiej karty z wyrazem. Każdy wyraz jest odczytywany. Kolejny ruch to odkrywanie trzeciej i czwartej karty. W ten sposób odsłuchasz wszystkie wyrazy. Nawigacja z poziomu klawiatury za pomocą strzałek, odsłuchiwanie wyrazów enterem lub spacją. Znajdź wszystkie pary wyrazów.

Glossary

acting point
acting point

punkt przyłożenia

Rbpqzwxktx0xY1
wymowa w języku angielskim: acting point
action
action

akcja

RhT1kE20guzux1
wymowa w języku angielskim: action
action - reaction law
action - reaction law

zasada akcji i reakcji

Rhn2qzGRFYxdl1
wymowa w języku angielskim: action - reaction law
balancing of forces
balancing of forces

równoważenie sił

RqVH77GfYXbNA1
wymowa w języku angielskim: balancing of forces
direction
direction

zwrot

RpSOosSa5kz4D1
wymowa w języku angielskim: direction
force
force

siła

RUlvmaIEhzGub1
wymowa w języku angielskim: force
mutual interactions
mutual interactions

oddziaływanie wzajemne

R862ZjAJGkD5f1
wymowa w języku angielskim: mutual interactions
Newton’s third law
Newton’s third law

III zasada dynamiki Newtona

R13JaIve9WreR1
wymowa w języku angielskim: Newton’s third law
reaction
reaction

reakcja

R1RTEieTmCVSx1
wymowa w języku angielskim: reaction
resultant force
resultant force

siła wypadkowa

Rg2LKFSoplfDk1
wymowa w języku angielskim: resultant force

Keywords

actionactionaction

forceforceforce

mutual interactionsmutual interactionsmutual interactions

Newton’s third lawNewton’s third lawNewton’s third law

reactionreactionreaction