The goal of this activity is for students to understand the connection between constant velocity motion and zero velocity with balanced forces, and non-constant or accelerated motion with unbalanced forces.

In the Preliminary Observations, students observe an object moving under the influence of zero net force and an object moving under the influence of unbalanced forces. We recommend that you do this as a whole-class activity. Students then design an experiment and compile evidence for a connection between constant velocity and balanced forces as well as a connection between changing velocity and unbalanced forces.


  • Design and perform an investigation; draw a conclusion from evidence
  • Identify constant velocity motion and motionlessness as an indication of balanced forces
  • Identify any change in velocity (speed or direction) with unbalanced forces