I do this activity with all levels of first year physics (freshman general science, junior conceptual and accelerated). I use it to introduce the connection between unbalanced (net) forces and accelerations before any formal introduction of Newton's 2nd Law. Students use spring scales to give "elevator rides" to masses and look at the apparent weight of the mass at each point in the ride. They then connect what they saw in the lab with their "everyday" experience of riding in an elevator. I have found it works best to have students work in pairs so one can watch the scale as the other pulls it up and down.
There is no math in this lab, it is all purely observation and reflection.
Depending on the level of detailed reflection that the students will engage in, this activity can take 20-30 minutes.