# Measuring friction coefficient with a inclined plane. Beetle problem

I want to measure friction coefficient between a beetle and an inclined plane (angle of inclination $\theta$). As we all know, friction coefficient $\mu$ is given with: $\mu=tg \rho$, where $\rho$ is the angle of sliding down monotonically. Is it sufficient to just put a beetle on the plane and slowly increase $\theta$ and see at which angle will it slide down? Or do I need to take into account something more? Is my experiment too simple?

I'm asking because I have seen some beetles trapped in a glass bottle. I would like to know more about beetle's possibilities to escape from such trap. I want to know about how should be a bottle shaped and what is the best material to make escape easy for the beetle.

• What the angle limit will measure is the static friction, i.e. how much force it takes to "unstick" the beetle. Once the beetle is sliding, the kinetic friction will kick in, which is usually smaller than the static friction. You also have to be aware that both depend on the material of the plane. Are you planning different experiments with different beetles and materials? Commented Sep 22, 2015 at 20:50
• @CuriousOne I just want to know how should be a glass bottle shaped to allow a beetle to escape from it in as many bottle's positions as possible. Commented Sep 22, 2015 at 21:04
• I see. Most importantly for the shape there can't be any overhangs and the angles should be shallow, like in a bowl. I can tell you from observations that I have seen insects and spiders trapped by very shallow slippery surfaces, though, so changing just the shape of a bottle won't help much. What I usually do to allow them to escape (without having to be there myself to help) is to hang a piece of rough paper along the side of the container all the way to the top, that way the critters have a non-slippery surface to hold on to and they usually find their way out of the trap by themselves. Commented Sep 22, 2015 at 21:11
• @CuriousOne I'm also thinking about bottle's material. It would be fun if bottles were made of glass that would be "frictionfull" enough to allow insects escape. This means I should measure "the friction of insect walking" on different glasses. Commented Sep 22, 2015 at 21:16
• The friction with glass is mostly given by the surface roughness, but even rough glass may not be enough for insects to hold on to. Their feet are made for natural materials and they usually have small hooks and suckers that help them to stick to leaves etc.. Those don't work well on glass. Give it a try and see how the beetles are doing. You will learn quickly what works and what doesn't. Commented Sep 22, 2015 at 21:25