3.3

## UNSW Sydney

Skip to 0 minutes and 9 secondsEarlier we asked, why can't we analyse this simple suspended system using what we've learned already? These experiments will set the scene for finding an answer. From week 2, we'll need our force transducers, the load pans and washers, and the ruler. We'll hang the transducers from the support beam, using the supporting chairs as before.

Skip to 0 minutes and 38 secondsFor our rigid object, we cut this shape out of thick cardboard. Corrugated is good, making it as symmetrical as possible. Download the details, if you want to do this yourself. And we made a hook with paperclips.

Skip to 0 minutes and 56 secondsWe made holes in the cardboard so we can use the force transducers from week 2 to suspend it from the support beam. One hole is on the vertical centre line, and there are two holes either side of it, as symmetrical as possible. We'll be suspending a weight pan from the bottom of the shape. We'll need one hole on the bottom on the centre line, and one offset. Here's how to set it up. We suspend the cardboard shape from the force transducers, positioning them so they are vertical, and then readjust the string until the top of the cardboard is horizontal. That looks about right. Now we are ready for the measurements.

Skip to 1 minute and 40 secondsFirst we'll weigh the cardboard shape by finding the force in each force transducer in the usual way, and recording the result. That's the first experiment.

Skip to 1 minute and 54 secondsFor the second experiment, we'll hang a loaded pan from the centre bottom hole and repeat the measurements. For the final experiment with this set up, we'll move the loaded pan and weights to the offset hole. The cardboard has rotated. Did you expect that? Anyway, adjust it to be square again before measuring and recording the forces. That's the third and final experiment in this set. Next, we'll look at generating a pure torque.

# Experiments on a rigid object

Trust us. Although the significance of twist mightn’t be an obvious part of these experiments, when you come to analyse them twist is vital.

If you have already made the force transducers you’ve got most of the kit you need, and the experiments won’t take long. If you haven’t made the rubber band transducers, it’s not too late. Why not make them now.

You’ll get a physical appreciation of the importance of considering twist. And you’ll be ready for the next experiments.

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).

If you don’t have access to a camera, we encourage you to still do the activity and write a description of your experiment on the Padlet wall.

For a guide to using Padlet, please see FutureLearn’s social media help page.