Module P3: Forces for Transport P3g: Falling Safely Falling objects are usually subject to at least two forces - weight and drag. Some cars have similar engines to others yet have very different top speeds. This is to do with pairs of forces which may or may not balance. These ideas are of vital importance to the parachutist and drag-racer who want to slow down in time - safely! Investigating falling whirligig, parachutes or plasticine shapes provides the opportunity to explain phenomena by developing and using scientific theories. Work on the balance of forces illustrates the use of modelling in developing scientific understanding. GRADE G - D GRADE C GRADE B A* Targets for Improvement – Recognise that frictional forces (drag, Explain in terms of the Explain, in of balance of forces, friction, air resistance): balance of forces how why objects reach a terminal speed: act against the movement moving objects: higher speed = more drag • • lead to energy loss and inefficiency increase speed larger area = more drag • • • can be reduced (shape, lubricant). decrease speed weight (falling object) or driving • • • maintain steady force (e.g. a car) = drag when • Explain how objects falling through the speed. travelling at terminal speed. Earth’s atmosphere reach a terminal speed. Understand why falling objects do not Recognise that Understand that gravitational field experience drag when is no acceleration due to strength or acceleration due to atmosphere. gravity (g) is the same gravity: for any object at a is unaffected by atmospheric • given point on the changes Earth’s surface. varies slightly at different points on • the surface will be slightly different on the top of • a mountain or down a mineshaft.
Module P3: Forces for Transport P3g: Falling Safely Falling objects are usually subject to at least two forces - weight and drag. Some cars have similar engines to others yet have very different top speeds. This is to do with pairs of forces which may or may not balance. These ideas are of vital importance to the parachutist and drag-racer who want to slow down in time - safely! Investigating falling whirligig, parachutes or plasticine shapes provides the opportunity to explain phenomena by developing and using scientific theories. Work on the balance of forces illustrates the use of modelling in developing scientific understanding. GRADE G - D GRADE C GRADE B – A* Targets for Improvement Recognise that frictional forces (drag, friction, air resistance): • act against the movement • lead to energy loss and inefficiency • can be reduced (shape, lubricant). Explain how objects falling through the Earth’s atmosphere reach a terminal speed. Explain in terms of the balance of forces how moving objects: • increase speed • decrease speed • maintain steady speed. Explain, in of balance of forces, why objects reach a terminal speed: • higher speed = more drag • larger area = more drag • weight (falling object) or driving force (e.g. a car) = drag when travelling at terminal speed. Understand why falling objects do not experience drag when is no atmosphere. Recognise that acceleration due to gravity (g) is the same for any object at a given point on the Earth’s surface. Understand that gravitational field strength or acceleration due to gravity: • is unaffected by atmospheric changes • varies slightly at different points on the surface • will be slightly different on the top of a mountain or down a mineshaft.
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