(PP2) hooke’s law

• To investigate experimentally the extension of a spring and how it is related to the applied force, and recall that the extension of a spring is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.
• independent variable is the stretching force F. This is the weight attached to the spring and is calculated using W = mg.
• dependent variable is the extension of the spring e.
• control variables: the material of the spring, and the cross section area of the spring. These are kept the same by not changing the spring during the experiment.
• prediction - as the stretching force (i.e. the weight attached to the spring) increases, the extension of the spring will also increase.
• The greater the stretching force the greater the separation of the atoms of the spring. This will result in the spring having greater length and so greater extension.
• The main cause of error in this experiment is reading the stretched length of the spring.

  The metre rule scale should be read at eye level directly opposite the pointer.

  Use the slotted base to ensure that the metre rule is vertical.
• Stretching force F=spring constant k x extension e

  F = ke
• The gradient of the graph = stretching force F / extension e = spring constant k
•  as the stretching force increases the extension of the spring also increases.

  Line of best fit is a straight line through the origin, up to a certain point.

  We can say that the stretching force F is directly proportional to the extension e up to a limit known as the limit of proportionality.

  This is known as Hooke’s law.