Forces And Their Interactions
Resumen
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.
Objetivos
- 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.
Mapa mental
Este tema esta esquematizado para ver como se conectan las ideas.
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Nota de la lección
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Evaluación de la lección
Felicitaciones por completar la lección del Forces And Their Interactions. Ahora que has explorado el conceptos e ideas clave, es hora de poner a prueba tus conocimientos. Esta sección ofrece una variedad de prácticas Preguntas diseñadas para reforzar su comprensión y ayudarle a evaluar su comprensión del material.
Te encontrarás con una variedad de tipos de preguntas, incluyendo preguntas de opción múltiple, preguntas de respuesta corta y preguntas de ensayo. Cada pregunta está cuidadosamente diseñada para evaluar diferentes aspectos de tu conocimiento y habilidades de pensamiento crítico.
Utiliza esta sección de evaluación como una oportunidad para reforzar tu comprensión del tema e identificar cualquier área en la que puedas necesitar un estudio adicional. No te desanimes por los desafíos que encuentres; en su lugar, míralos como oportunidades para el crecimiento y la mejora.
- 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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