CORE Physics (Short Course) - 9223 OxfordAQA

Forces And Their Interactions

Akopọ

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.

Awọn Afojusun

  1. Objects interact by non-contact (field) forces (including gravity, electrostatics, magnetism) and by contact forces (including friction, air resistance, tension and normal contact force).
  2. Friction is a force between two surfaces, which impedes motion and may result in heating. Air resistance is a form of friction.
  3. 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.
  4. A force applied to an elastic object such as a spring will result in the object stretching and storing elastic potential energy.
  5. 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.

Àwòrán ọpọlọ

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Akọ̀wé Ẹ̀kọ́

A magnet lowered towards a steel paperclip does nothing at all until, at some particular height, the clip suddenly leaps off the bench and sticks. There was no moment of contact. Whatever acted on that clip crossed an air gap to do it. Now put the clip back on the bench and leave it alone: gravity is pulling it downwards every second, yet it does not move, which means something must be pushing back up on it with exactly as much force. Neither of those situations makes sense until you can name the forces involved and say which object each one acts on.

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Oriire fun ipari ẹkọ lori Forces And Their Interactions. Ni bayi ti o ti ṣawari naa awọn imọran bọtini ati awọn imọran, o to akoko lati fi imọ rẹ si idanwo. Ẹka yii nfunni ni ọpọlọpọ awọn adaṣe awọn ibeere ti a ṣe lati fun oye rẹ lokun ati ṣe iranlọwọ fun ọ lati ṣe iwọn oye ohun elo naa.

Iwọ yoo pade adalu awọn iru ibeere, pẹlu awọn ibeere olumulo pupọ, awọn ibeere idahun kukuru, ati awọn ibeere iwe kikọ. Gbogbo ibeere kọọkan ni a ṣe pẹlu iṣaro lati ṣe ayẹwo awọn ẹya oriṣiriṣi ti imọ rẹ ati awọn ogbon ironu pataki.

Lo ise abala yii gege bi anfaani lati mu oye re lori koko-ọrọ naa lagbara ati lati ṣe idanimọ eyikeyi agbegbe ti o le nilo afikun ikẹkọ. Maṣe jẹ ki awọn italaya eyikeyi ti o ba pade da ọ lójú; dipo, wo wọn gẹgẹ bi awọn anfaani fun idagbasoke ati ilọsiwaju.

  1. Which of these is a non-contact force? A. Friction B. Tension C. Magnetism D. Normal contact force Answer: C
  2. 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
  3. 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
  4. 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
  5. 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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