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Students then begin the For You To Do activity.

In this activity, students weigh a box with a spring scale and measure the force required to pull it across a table at constant speed. By adding sand to the box, they take repeated measurements of weight and frictional force. A graph then shows them that the frictional force is directly proportional to the weight-more weight, more friction. An earlier activity convinced students that all objects weigh less on the moon. And so they can now conclude that friction must be less on the moon.