# Experiment: Force transducers

Forces generated in an earthquake can destroy entire cities, so it might seem odd to say that they are just an abstract construct.

Forces generated in an earthquake can destroy entire cities, so it might seem odd to say that they are just an abstract construct. More on that in the analysis activities.

For now, we need a way of detecting a force, measuring how big it is and specifying the direction it acts in. For this we need a transducer – a device that converts something we can’t measure into something else that we can.

Our force transducers will be based on the chain of rubber bands that we made during the experiment in Week 1. To help keep creep under control we will minimise the time between loading up and measuring.

If you didn’t do the Week 1 experiments it’s not too late to do them now. It would be a good investment because you can use the transducers this week and next.

Before SI units were common the unit of force was often the weight of a standard mass. In some places it still is, for example the unit of mass in US customary units is the pound (the pound mass), and the unit of force is the weight of a pound mass (the pound weight). We’ll have more on weight later. Mostly with US customary units the term ‘pound’ is used for both mass and weight, leaving you to work out what is meant from the context. This can be confusing but it won’t affect us much because we’ll generally use SI units, where the unit of mass is the kilogram and the unit of force is the Newton.

Once we have our transducers we’ll use them to find out how forces add.

### Talking points

• Did you think of the effect of creep when the transducer was calibrated and used?
• Was I being hopeful when I suggested that a precision of +/- 1 mm was possible using the rule?
• Did it seem odd to have the weight of a “washer” as the unit of force?

If you attempt the experiment, take a photo and upload it to our Through Engineers’ Eyes Padlet wall. You can include a link to your photo in the comments for this step (click on your post on the Padlet wall and then copy the web address).