A pedal bin has a spring that is stretched when the pedal is pressed. The extension of the spring is 0.040 m when the pedal is fully pressed.

The mechanism will work correctly if the spring:

has a linear force-extension relationship up to an extension of 0.040 m
stores at least 0.50 J at this extension, so that the lid closes
exerts no more than 32 N at this extension, so that the mechanism is not overloaded.

The table gives test information for three springs.

Spring	Test information
P	Its force-extension relationship becomes non-linear at an extension of 0.030 m.
Q	Its spring constant is 750 N/m. At an extension of 0.040 m, it exerts a force of 30 N. Its limit of proportionality is 40 N.
R	Its force-extension relationship is linear up to 0.040 m. At this extension, it exerts a force of 36 N and stores 0.72 J.

Use the equation

$E=12×k×x2\displaystyle E=\frac{1}{2}\times k\times x^2$

A pedal bin has a spring that is stretched when the pedal is pressed. The extension of the spring is 0.040 m when the pedal is fully pressed.

The mechanism will work correctly if the spring:

has a linear force-extension relationship up to an extension of 0.040 m
stores at least 0.50 J at this extension, so that the lid closes
exerts no more than 32 N at this extension, so that the mechanism is not overloaded.

The table gives test information for three springs.

Spring	Test information
P	Its force-extension relationship becomes non-linear at an extension of 0.030 m.
Q	Its spring constant is 750 N/m. At an extension of 0.040 m, it exerts a force of 30 N. Its limit of proportionality is 40 N.
R	Its force-extension relationship is linear up to 0.040 m. At this extension, it exerts a force of 36 N and stores 0.72 J.

Use the equation

$E=12×k×x2\displaystyle E=\frac{1}{2}\times k\times x^2$

15.1 Forces and springs

15.1 Forces and springs Questions