Stress isn't only what you feel when you're studying for a big test. Objects experience stress, too, a different kind of stress! Objects can't feel anxious when they have a deadline, but they do feel pressure, which is a form of stress. Pressure is simply defined as a force spread out over an area.

In the first part of this activity you used one hand and one finger to apply the same amount of force to your legs, and you felt a difference in pressure. The forces were the same, but the area with which you applied the force over was different. Your whole hand has a much greater area than one fingertip! Here's the equation: Force / Area = Pressure (Stress) As the area gets bigger, the pressure gets smaller. But if the force gets bigger, the pressure also gets bigger. If you were to press harder on your legs with your hand and finger, the pressure should increase on both legs.

In the second part of the activity, you explored how a sheet of paper is affected by different stresses. The first attempt to tear the paper was probably more difficult than the second. In the second attempt, you made a stress concentration in the paper when you made the tear. This means that you made an area in the paper where the area was much smaller and therefore the pressure or stress in the paper was much higher, and made it easier to tear!

So now you can see that pressure and stress aren't just experienced by people, but also by objects. You can cause something to feel much higher stresses by decreasing the area which distributes the forces.