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GCSE Physics · key term
A straight line that touches a circle at one point; an object's instantaneous velocity in circular motion is directed along a tangent.
Used by AQA, Edexcel and OCR
Specification 4.5.6.1.4 · Paper 2
A straight line drawn to touch a curve at a chosen point and match its slope there.
Revise: The distance–time relationshipTo find the speed at a chosen time, draw a straight tangent that just touches the curve at that point and follows its local slope. Calculate the tangent’s gradient using two convenient, well-separated points on the tangent. The result is the speed at that moment.
Specification 2.7, 2.20, 2.21 · Paper 1
Choose two well-separated points on the line or tangent when calculating a gradient; they need not both be measured points.
Choose two well-separated points on the line or tangent; this reduces the effect of reading uncertainty.
For a curved section, do not join the point to the origin unless the question asks for an average from the start. Draw a tangent at the required point for instantaneous speed.
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A straight line drawn at a point on a curve so that it has the same local gradient as the curve there.
On a curved graph, the speed at one particular instant is found from the gradient of a tangent. The tangent is a straight line drawn through the chosen point so that it matches the curve's direction there.
A straight line that touches a circle at one point; at that point it is perpendicular to the radius.
Specification P2.2q · Paper 1 (Foundation), Paper 3 (Higher)
A straight line that touches a circle at one point. The instantaneous velocity of an object in circular motion is directed along a tangent.
Revise: Circular motionThe instantaneous velocity arrow is always tangent to the circle: it points in the direction in which the object is moving at that instant. It does not point towards the centre. Equal-length arrows can represent constant speed, while their changing orientations show changing velocity.
Paper 1, Paper 2
The straight line that touches a curve at one chosen point and has the same gradient as the curve there.
Revise: Analyzing Motion with GraphsTo estimate the speed at one particular instant, draw a tangent to the curve at that point. Choose two widely separated points on the tangent—not necessarily points on the original curve—and calculate its gradient. This gives the instantaneous speed at that time.