# Marvelous Machines: Making Work Easier

## Using Simple Machines (3) / Grade 5 / Wilmington, NC

The EIE Curriculum

## EiE - Marvelous Machines: Making Work Easier, L3 Part 3

Students use simple machines and spring scales to determine how much force is needed to move a standard load and think about the ergonomics of using each machine.

### What evidence do you see that Ann's students are beginning to develop an understanding that all simple machines have advantages and disadvantages?

When Ann poses the idea of the "best" simple machine, students are able to point out that it really depends on what job you're trying to do; there are trade-offs for all of the machines.

• A student points out that the best machine depends on what the job is. Ann guides the class to discuss the idea that moving something horizontally may require a different simple machine than lifting something vertically. (2:43)
• Ann guides students to think through the differences in the trade-offs of the single and double pulleys. A student shares that there was more rope with the double pulley, but less force was required. (4:37)
• After students complete the hands-on activity, Ann reminds them of the formula "work=force x distance." One student points out that based on the equation, if the force is greater, you have to have a lower number for distance (or the opposite). (7:34)