Teaching Levers and Pulleys?

Are your students trying to use a spring scale to measure force? Try this tutorial, Virtual Spring Scale,  to develop their abilities.  Simulating an actual spring scale, the Virtual Spring Scale allows students to measure the force in Newtons of a set of items. They can hang objects from the spring scale and use the spring scale to drag objects across a flat surface or up an inclined plane at various degrees. I used this interactive before we began our first experiment in the Foss kit, Levers and Pulleys.  It made a world of difference during the experiment.