Forces, Movement, Shape And Momentum
Aperçu
Every time a footballer strikes a ball, a car brakes at a junction, or a bungee cord stretches under a jumper's weight, forces are at work. This topic brings together the rules that govern how objects move, change shape, and interact, from Newton's celebrated laws to the conservation of momentum that protects passengers in modern vehicles.
You will calculate resultant forces and accelerations, distinguish weight from mass, analyse stopping distances and terminal velocity, explore how springs stretch under load, and apply the momentum equation to collisions and safety design. The topic closes with moments, pivots, and the centre of gravity, completing the mechanics toolkit you need for both Edexcel papers.
Objectifs
- Describe the effects of forces between bodies such as changes in speed, shape or direction
- Identify different types of force such as gravitational or electrostatic
- Understand how vector quantities differ from scalar quantities
- Understand that force is a vector quantity
- Calculate the resultant force of forces that act along a line
- Know that friction is a force that opposes motion
- Know and use the relationship between unbalanced force, mass and acceleration: force = mass x acceleration, F = m x a
- Know and use the relationship between weight, mass and gravitational field strength: weight = mass x gravitational field strength, W = m x g
- Know that the stopping distance of a vehicle is made up of the sum of the thinking distance and the braking distance
- Describe the factors affecting vehicle stopping distance, including speed, mass, road condition and reaction time
- Describe the forces acting on falling objects and explain why falling objects reach a terminal velocity
- Investigate how extension varies with applied force for helical springs, metal wires and rubber bands
- Know that the initial linear region of a force-extension graph is associated with Hooke's law
- Describe elastic behaviour as the ability of a material to recover its original shape after the forces causing deformation have been removed
- Know and use the relationship between momentum, mass and velocity: momentum = mass x velocity, p = m x v
- Use the idea of momentum to explain safety features
- Use the conservation of momentum to calculate the mass, velocity or momentum of objects
- Use the relationship between force, change in momentum and time taken: force = change in momentum / time taken, F = (mv - mu) / t
- Demonstrate an understanding of Newton's third law
- Know and use the relationship between the moment of a force and its perpendicular distance from the pivot: moment = force x perpendicular distance from the pivot
- Know that the weight of a body acts through its centre of gravity
- Use the principle of moments for a simple system of parallel forces acting in one plane
- Understand how the upward forces on a light beam, supported at its ends, vary with the position of a heavy object placed on the beam
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Évaluation de la leçon
Félicitations, vous avez terminé la leçon sur Forces, Movement, Shape And Momentum. Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à lépreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.
Vous rencontrerez un mélange de types de questions, y compris des questions à choix multiple, des questions à réponse courte et des questions de rédaction. Chaque question est soigneusement conçue pour évaluer différents aspects de vos connaissances et de vos compétences en pensée critique.
Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.
- A resultant force acts on an object. What will happen to the object? A) It will remain stationary B) It will accelerate in the direction of the resultant force C) It will move at constant velocity D) It will decelerate in all cases Answer: B
- An astronaut has a mass of 80 kg. What is their weight on Earth where g = 10 N/kg? A) 8 N B) 80 N C) 800 N D) 8000 N Answer: C
- Which of the following increases the braking distance of a vehicle? A) Better tyres B) A dry road surface C) A higher speed D) A shorter reaction time Answer: C
- A spring obeys Hooke's law. When a force of 4 N is applied, the extension is 2 cm. What is the extension when 10 N is applied? A) 3 cm B) 5 cm C) 8 cm D) 10 cm Answer: B
- Two ice skaters push apart from rest. What is the total momentum of the two skaters after they separate? A) Greater than before B) Zero C) Equal to the momentum of the heavier skater D) Impossible to determine Answer: B
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Section de manuel
Newton’s Second Law of Motion: Concept of a System
Newton’s second law of motion is closely related to Newton’s first law of motion. It mathematically states the cause and effect relationship between force and changes in motion. Newton’s second law of motion is more quantitative and is used extensively to calculate what happens in situations involvi
"College Physics: Newton’s Second Law of Motion: Concept of a System" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/4-3-newtons-second-law-of-motion-concept-of-a-system. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
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Section de manuel
Normal, Tension, and Other Examples of Forces
Forces are given many names, such as push, pull, thrust, lift, weight, friction, and tension. Traditionally, forces have been grouped into several categories and given names relating to their source, how they are transmitted, or their effects. The most important of these categories are discussed in
"College Physics: Normal, Tension, and Other Examples of Forces" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/4-5-normal-tension-and-other-examples-of-forces. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
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