Forces And Their Interactions
Übersicht
Hold a magnet a centimetre above a steel paperclip and the clip jumps up to meet it. Nothing touched it. Rest the same clip on a table instead and it sits there, perfectly still, even though gravity is pulling on it the whole time. Two everyday moments, two completely different ways for one object to act on another, and between them they contain most of what this lesson is about.
You will sort every force you meet into the ones that need contact and the ones that reach across a gap, and learn why a force is never something an object simply has. Then you will put a number on gravity itself, work out what you would weigh standing on the Moon without changing your mass by a single gram, and stretch a spring far enough to find the point where it stops behaving itself. This is the first topic of the course, and almost everything that follows leans on it.
Ziele
- Objects interact by non-contact (field) forces (including gravity, electrostatics, magnetism) and by contact forces (including friction, air resistance, tension and normal contact force).
- Friction is a force between two surfaces, which impedes motion and may result in heating. Air resistance is a form of friction.
- Weight is the force acting on an object due to gravity. The weight of an object depends on the gravitational field strength at the point where the object is. The weight of an object can be calculated using the equation: Weight (N) = mass (kg) × gravitational field strength (N/kg) W=m×g Students will not be expected to know the value of g; it will be given in any examination items.
- A force applied to an elastic object such as a spring will result in the object stretching and storing elastic potential energy.
- For an object behaving elastically, the extension is directly proportional to the force applied, provided that the limit of proportionality is not exceeded. The relationship between the force, F, and the extension, e, is: F=k×e where k is a constant. Required practical: Investigate the relationship between force and extension for a spring.
Mindmap
Dieses Thema ist als Karte dargestellt, damit die Zusammenhange sichtbar werden.
Mindmap in der App offnen
Lektionshinweis
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Unterrichtsbewertung
Herzlichen Glückwunsch zum Abschluss der Lektion über Forces And Their Interactions. Jetzt, da Sie die wichtigsten Konzepte und Ideen erkundet haben,
Sie werden auf eine Mischung verschiedener Fragetypen stoßen, darunter Multiple-Choice-Fragen, Kurzantwortfragen und Aufsatzfragen. Jede Frage ist sorgfältig ausgearbeitet, um verschiedene Aspekte Ihres Wissens und Ihrer kritischen Denkfähigkeiten zu bewerten.
Nutzen Sie diesen Bewertungsteil als Gelegenheit, Ihr Verständnis des Themas zu festigen und Bereiche zu identifizieren, in denen Sie möglicherweise zusätzlichen Lernbedarf haben.
- Which of these is a non-contact force? A. Friction B. Tension C. Magnetism D. Normal contact force Answer: C
- A box is pushed across a rough floor. Which statement about the friction acting on the box is correct? A. It acts in the direction the box is moving B. It impedes the motion of the box and may warm the surfaces C. It acts at right angles to the floor D. It acts only after the box has stopped moving Answer: B
- An object has a mass of 4.0 kg. The gravitational field strength is 10 N/kg. What is the weight of the object? A. 0.40 N B. 2.5 N C. 40 N D. 400 N Answer: C
- A force of 12 N stretches a spring by 0.30 m. The spring is behaving elastically. What is the spring constant of the spring? A. 0.025 N/m B. 3.6 N/m C. 40 N/m D. 360 N/m Answer: C
- For a spring behaving elastically, the extension is directly proportional to the force applied only up to a certain force. What is that force called? A. The weight B. The spring constant C. The tension D. The limit of proportionality Answer: D
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