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1.2.3Motion, Forces and Energy

Distance-Time Graphs — Cambridge IGCSE Physics 0625 Revision Notes & Topical Questions

5 min read 8 parts Lesson 14 of 91 1 quiz

📚 Cambridge IGCSE Physics 0625 Hub / Topical Revision
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Lesson summary

1.2.3 Distance-Time Graphs — IGCSE Physics Notes — IGCSE PHYSICS notes: Describe motion from distance-time graphs and calculate speed from the gradient.LineMeaningHorizontalStationary, speed zeroStraight with a gradientConstant speedSteeper slopeGreater speedShallower slopeLower …

  • Straight line
  • Accelerating
  • Increasing gradient
  • Decreasing gradient
  • Gradient triangle
  • Decelerating

Part 1 of 6Reading distance-time graphs

LineMeaning
HorizontalStationary, speed zero
Straight with a gradientConstant speed
Steeper slopeGreater speed
Shallower slopeLower speed
Curve with increasing gradientSpeeding up
Curve with decreasing gradientSlowing down

Part 2 of 6Constant speed

Straight line
  • Straight line the object moves at constant speed
Stationary
  • Stationary a horizontal line means distance does not change
Gradient
  • Gradient it represents the speed of the object

Part 3 of 6Changing speed

Accelerating
  • Accelerating the distance-time graph is curved
Increasing gradient
  • Increasing gradient speed increases with time
Decreasing gradient
  • Decreasing gradient speed decreases with time

Part 4 of 6Plotting a distance-time graph

1
Label the x-axis with time and the y-axis with distance.
2
Choose sensible scales so the graph fills more than half of the grid.
3
Plot the points from the data.
4
Join with straight lines if the speed is constant or with a curve if it changes.

Part 5 of 6Speed from the gradient

Equation
  • Equation speed = gradient = Δy ÷ Δx
Δy
  • Δy the change in distance
Δx
  • Δx the change in time
Gradient triangle
  • Gradient triangle draw the largest possible one on a straight section
Units
  • Units check the axis units, which may be km and minutes rather than m and s

Part 6 of 6More from the specification

1Interpretation of Distance-Time Graphs
  • On a distance-time graph, the gradient represents the speed of the moving object,
  • where a steeper slope indicates faster motion, a horizontal line represents zero speed at rest,
  • and the total distance travelled is measured directly from the vertical axis.
2Speed-Time Graphs and Acceleration
  • On a speed-time or velocity-time graph, the slope represents acceleration,
  • and the area under the graph represents total distance travelled;
    • a constant positive slope indicates uniform acceleration in the positive direction.
3Scalar Speed vs Vector Velocity
  • Speed is a scalar quantity measuring rate of distance covered,
    • (average speed = total distance / total time)
  • whereas velocity is a vector possessing both magnitude and a defined direction.
4Balanced Forces and Terminal Motion
  • When an object falls, downward weight is opposed by air resistance;
  • when these opposing forces balance, the net force is zero and the object continues falling at a constant terminal velocity.
5Gravitational field
  • Region where mass experiences gravitational force.
6Field strength
  • G = Fg/m.
7Velocity
  • Rate of change of displacement.
8Resistance
  • Opposition to current, R = V / I, in ohms (Ω).
9Weight
  • Gravitational force on a mass.
10Terminal
  • Connection point of a cell, labelled + or −.
11Speed-time graph
  • Graph of speed against time.
12Average speed
  • Total distance divided by total time.
13Terminal velocity
  • Constant speed when air resistance equals weight.
14Resultant force
  • Another name for net force.

Key terms

TermMeaning
Distance-time graphGraph of distance against time.
GradientSteepness of a line, Δy ÷ Δx.
StationaryNot moving.
Constant speedSpeed that does not change.
AcceleratingSpeeding up.
DeceleratingSlowing down.

Avoid these mistakes

1
Thinking a horizontal line is constant speed — it is stationary.
2
Thinking a steeper curve means distance is larger — it means speed is higher.
3
Using the whole line when only one section is asked — use only that straight section.
4
Ignoring axis units — check whether the units are standard.

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