Speca › Topics › GCSE Combined Science

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• Assessment mark schemeWord, editable
• End-of-topic assessmentWord, editable
• HomeworkWord, editable
• Retrieval-practice quizzesWord, editable
• SlidesPowerPoint, editable
• Starter & exit ticketWord, editable
• Tiered worksheetWord, editable
• Worksheet mark schemeWord, editable

Foundation and Higher tier

• Distinguish scalar quantities (magnitude only) from vector quantities (magnitude and direction), and represent a vector quantity with an arrow whose length shows magnitude and direction shows direction.
• Define a force as a push or pull arising from an object's interaction with another object, and distinguish contact forces (objects physically touching, e.g. friction, air resistance, tension, normal contact force) from non-contact forces (objects physically separated, e.g. gravitational, electrostatic, magnetic force); describe the interaction between a pair of objects that produces a force on each, representing these forces as vectors, and know force itself is a vector quantity.
• Define weight as the force on an object due to gravity, explain that it depends on the gravitational field strength at the object's location, use W = m × g (weight in newtons; mass in kilograms; gravitational field strength in N/kg, always supplied), explain that an object's weight can be treated as acting at a single point (its centre of mass), that weight and mass are directly proportional, and that weight is measured with a calibrated spring balance (newtonmeter).
• Explain that several forces acting on an object can be replaced by a single equivalent resultant force, and calculate the resultant of two forces acting in a straight line.
• Explain that a force causes work to be done on an object when it causes the object to move (be displaced), use W = F × s (work done in joules; force in newtons; distance moved along the force's line of action in metres), know that 1 joule = 1 newton-metre and convert between the two units, describe the energy transfer involved when work is done, and explain that work done against friction raises an object's temperature.
• Give examples of the forces involved in stretching, bending, or compressing an object, explain why changing a stationary object's shape this way requires more than one force to be applied, and describe the difference between elastic deformation (the object returns to its original shape) and inelastic deformation (it doesn't).
• Explain that an elastic object's extension is directly proportional to the applied force, provided the limit of proportionality isn't exceeded, and use F = k × e (force in newtons; spring constant in N/m; extension in metres): this relationship also applies to compression, where e becomes the compression amount.
• Explain that a force stretching or compressing a spring does work, storing elastic potential energy, and that (provided the spring isn't inelastically deformed) the work done and the energy stored are equal; describe the difference between a linear and a non-linear force-extension relationship, calculate a spring constant in linear cases, interpret force-extension investigation data, and calculate the work done stretching/compressing a spring (up to the limit of proportionality) using Eₑ = ½ × k × e² (supplied on the physics equation sheet), calculating relevant stored-energy and energy-transfer values.

Higher tier only

• Describe the forces acting on an isolated object or system, and use free body diagrams to describe qualitatively how several forces combine into a resultant force on an object, including balanced-force (zero resultant) situations.
• Explain that a single force can be resolved into two components acting at right angles to each other, with the same combined effect as the original force, and use vector diagrams (scale drawings) to illustrate force resolution and equilibrium situations, and to determine a resultant force's magnitude and direction.

Required practicals

• Required practical 18: investigate the relationship between force and extension for a spring.

Where students go wrong

• Confusing mass and weight, particularly treating them as interchangeable, rather than understanding weight is a force (dependent on gravitational field strength, in newtons) while mass is a fixed amount of matter (in kilograms).
• Assuming a stationary object under multiple forces has "no forces acting," rather than understanding balanced forces (zero resultant) are still forces, just cancelling out.
• Believing all deformation is elastic, rather than distinguishing elastic (returns to original shape) from inelastic (doesn't) deformation, and recognising the extension-force proportionality only holds up to the limit of proportionality.
• Forgetting work is only done when a force causes actual displacement in the direction of the force: a force applied to a stationary object does no work in the physics sense, even if it "feels like effort."
• (Higher tier) Resolving a force into components that don't actually reconstruct the original force when combined: a common scale-drawing/arithmetic error rather than a conceptual one.

How it gets asked in the exam

"Calculate the weight of...", "Describe the forces acting on...", "Calculate the work done when...", "Explain the difference between elastic and inelastic deformation", "Calculate the spring constant from the graph", "Calculate the elastic potential energy stored in...", "Use a scale diagram to find the resultant force" (Higher).

Key vocabulary

Scalar, vector, resultant force, contact force, non-contact force, weight, centre of mass, work done, elastic deformation, inelastic deformation, spring constant, elastic potential energy, equilibrium (HT), resolution of forces (HT).

Assumed prior knowledge

• Basic algebraic rearrangement and substitution, needed for the weight, work-done, spring-force, and elastic-potential-energy equations.
• Elastic potential energy's equation already appears in Energy (this taxonomy's topic 18); this topic adds the physical spring-force reasoning behind it.
• KS3-level familiarity with the idea that forces can push, pull, stretch, and squash objects.

How Speca scaffolds this topic

• A single, consistently drawn force-arrow convention (arrow length = magnitude, direction = force direction, labelled with name and value) used across every diagram in this topic, so reading force diagrams becomes a transferable skill rather than a new convention each time.
• A shared contact/non-contact force sorting table, built with real named examples (friction, tension, gravity, magnetism, etc.), reinforces the touching/not-touching distinction as the actual sorting rule rather than a memorised list.
• Force-extension graphs benefit from a consistent template showing the straight-line (proportional) region clearly distinguished from where the line curves (limit of proportionality exceeded), since correctly identifying that boundary is central to both the spring-constant and elastic-potential-energy calculations.
• (Higher tier) Force resolution and free body diagrams benefit from a fixed grid/protractor template used for every scale drawing, since accuracy in these diagrams depends heavily on consistent, careful drawing technique rather than conceptual understanding alone.

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