Pulley which way to go video

Its strength captures our imagination, like a bug in a cobweb. New research suggests these exaggerated pop culture depictions aren't so far from reality. Using their webs and a technique known as "lifting hunting," spiders really can trap foes up to 50 times heavier than themselves. A new study published in the Journal of the Royal Society Interface describes spiders in the Theridiidae family.

These critters use a unique "pulley" system of numerous silk threads — known as a tangle web — to lift their prey up to a height difficult to escape. This research is yet "another example of how spiders use their silks as external tools to overcome muscle limits," co-author Gabriele Greco tells Inverse. Greco is a researcher in the engineering department at the University of Trento in Italy.

How they did it — Greco and co-author Nicola M. Pugno studied five different spiders from two species in the Theridiidae family: Steatoda paykulliana and Steatodatriangulosa.

The researchers placed each spider specimen in a plastic box at room temperature covered in black paper. Black paper was used so they could better see the spider's light silk strands. For prey, the researchers selected a cockroach Blaptica dubia from South and Central America.

This foe was chosen for its weight and size. Once released into the box, the scientists pressed record , and observed the ensuing battle. What's new — The purpose of the lifting hunt mechanism is to keep prey from escaping.

This means I can draw the following two force diagrams for the two masses. So, how do you find the acceleration of cart 1? It seems clear, right? You just need to find the tension in the string since that's the only force in the horizontal direction.

You could write:. If I know the tension, I can calculate the acceleration. Simple, right? Even simpler, the tension would just be equal to the gravitational force on the hanging mass m 2. This is not the correct way to solve this problem — I actually remember making this exact mistake when I was an undergraduate student.

But why is it wrong? If I just solved the problem the correct way, it wouldn't be that much fun. Instead, I am going to set up an experiment to show that the tension in the string isn't just the weight of mass 2. You can see the setup in the image above it's called a half Atwood machine in case you want to google the solution. Basically, I have a mass on a low friction track with a string connected over a pulley to a hanging mass.

Both masses have force sensors on them so that I can measure the tension in the string. Also, I can measure the position, velocity and acceleration of the cart using the Vernier motion encoding system. This is basically just series of lines on the track that the cart uses to determine its position and thus velocity and acceleration.

With a cart mass of grams mass 1 and a hanger mass of grams mass 2 , I get the following data. But why? Technical rescue teams respond when the situation is especially difficult and requires significant resources to be deployed.

For this reason, they often have to deal with unique, surprising, and complex systems and challenges. To carry out these time-sensitive missions, they must be able to count on equipment that performs well. That's why Petzl provides solutions that make their work easier, like the new range of SPIN high-efficiency pulleys with swivel. The SPIN L1D consists of a faceted sheave mounted on a single-direction ratcheting wheel, offering a high-efficiency hauling pulley, and adding friction for a more controlled descent.