Forces, Movement, Shape And Momentum
Visão Geral
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.
Objetivos
- 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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- 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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