Pulley

Purpose: The purpose of this lab was to observe the relationship between force and distance using the simple machines we built in class. My table and I built 3 pulleys (one string, two string, and four string) in an effort to compare the a length of string and the amount of force used to lift a brass mass. 


How?: Before we could begin gathering data, our group had to assemble our 3 pulleys. First, we assembled our one string pulley which allowed us to lift a 200 gram (g) mass 10 centimeters (cm) from the table, only using one Newton (N) of force. Then we measured the length of string we had to pull in order to raise the mass--we measured 20 cm. We then built a two string and 4 string pulley, and did the same experiment; however, this time we raised the mass 5 cm and measured how many Newtons required to hold it steady. 

Graph: After collecting the data, we determined that there is an inverse relationship between force and distance. This means that when we increase the amount of string used, there is a decrease in the amount of force needed and vice versa. By adding more wheels to the pulley, there is an increase in the number of strings, which in turn decreased the amount of force needed to lift the mass. 

To graph our data, we plotted Force in Newtons and Distance in Meters and from there, connected our point to our axis, making a rectangle which we colored in.

Real World: Attached is a link that explains the pulley system used in elevators. With equal loads on each side of the "sheave" in an elevator, it only takes a little bit of force to tip the balance one way or the other. The system is just like a see-saw in a park.

http://science.howstuffworks.com/transport/engines-equipment/elevator3.htm