This hands-on activity is an excellent introduction to Newton’s First Law, otherwise known as the Law of Inertia. Students learn that inertia is an object’s resistance to a change in motion. We begin this activity by having the class review the key terms of the lesson:
Inertia – resistance to a change in motion.
Newton’s First Law – an object at rest will remain at rest, and an object moving at a constant velocity will continue moving at a constant velocity, unless it is acted upon by an unbalanced force.
Equilibrium – When the net force on an object is zero. An object is in equilibrium if it is at rest or moving at a constant velocity.
Through discussion of these terms, students learn that if an object is at rest it will remain at rest unless an unbalanced force comes along and disturbs its equilibrium. Without the presence of an unbalanced force, the object will not experience a change in speed or direction. Additionally, objects with greater mass have greater inertia, which will come in handy during this activity.
The object of this activity is to observe the properties of Newton’s First Law by attempting to remove the notecards from a tower of wooden blocks without causing enough of a disturbance to the tower’s equilibrium to cause it to tumble. This is similar to another famous inertia demonstration; the tablecloth trick. That one can be found here (and is a fantastic demonstration to introduce the concepts with).
Because the cubes want to resist any change in motion due to their inertia, they will stay in place if the card is removed quickly enough. Try taking each notecard out separately, and once you have done this successfully, try again by having everyone in the group pull the cards out at the same time. Can it be done?… You’ll have to be very precise!
Try this again, but this time use the paper cups. The paper cups have less mass, and therefore less inertia. This means they will have less resistance to a change in motion, creating an even greater challenge!
This multi-sensory activity provides tactile and auditory feedback for students with visual impairments, and is further adapted for students with varying fine motor skills. The string is attached to each notecard so as to make pulling the card easier, as well an enabling a greater number of students to participate at the same time. The instructor may build/rebuild the towers during the activity, or may choose to let the students do so. If the students create a wobble, unbalanced tower, it leads to a discussion on the force causing a disturbance to its equilibrium, which in this case is gravity.
Also, one student suggested that the notecards should have physics quiz questions written on them for bonus points!