Process/graph pairs

Here is each graph matched to its process.

  • Temperature of a cup of tea over time.

    Decreasing curve with increasing gradient and y-intercept at 100
    Graph G

    Newton’s law of cooling says that the rate of cooling is proportional to the difference between the temperature of the object and the ambient temperature. Here the initial temperature is assumed to be \(100^{\circ}\)C, and the room temperature is \(20^{\circ}\)C.

  • Height of the valve on a bicycle tyre as the bicycle moves forwards.

    Wave oscillating between 0 and 0.65, and with period 2
    Graph C

    Measuring from the ground, the height of the valve oscillates between \(0\) and the diameter of the wheel.

  • Height of a tennis ball thrown straight up and then caught.

    Between 0 and 2 the curve is an upside down parabola, and after 2 the curve becomes a straight horizontal line
    Graph H

    Assuming constant acceleration due to gravity and neglecting factors such as air resistance leads to a parabola.

  • Distance fallen by a parachutist jumping out of a plane.

    Increasing curve with increasing gradient, that passes through the origin
    Graph D

    Near the start of the jump, long before the parachutist opens the parachute, air resistance is negligible and there is just the constant acceleration due to gravity to consider.

  • Reading on the odometer (mile counter) of a car driving on a motorway.

    Straight line with y-intercept at 3100,and positive gradient
    Graph A

    The speed of the car is fairly constant, so the distance travelled is a straight line graph.

  • Radius of a spherical balloon as it is inflated.

    Increasing curve with decreasing gradient, that passes through the origin
    Graph F

    The volume increases at a constant rate, so the radius increases like the cube root.

  • Volume of water remaining in a cup as water is sucked out through a straw.

    Straight line with y-intercept at 600 and negative gradient
    Graph B

    The water is removed at a constant rate, so the volume decreases linearly.

  • Distance along a tape measure measured in inches compared with distance measured in metres.

    Straight line with positive gradient passing through the origin
    Graph E

    There is a conversion factor between inches and metres, which leads to a straight line graph.