The Tablecloth Trick and Inertia

Procedure

1. Start with a mini-lesson about inertia. Here is some background information:

   As Newton's First Law of Motion states, an object in motion wants to stay in motion.
   When you are riding in a car, both you and the car are in motion. When the driver steps on the brakes, the brakes create friction with the car's tires, causing the car to slow down.
   
   Usually, if the car slows down gradually, you'll slow down with it. The friction of your legs against the seat, the seatbelt holding you down, your feet pressing against the floor, and other things combine to help you slow down.
   
   But if the car stops suddenly, inertia will cause you to keep going forward unless you are somehow tied down, like with a seatbelt.
   
   So, because of inertia, it's important to wear your seatbelt when you ride in a car, to make sure that you stop when the car stops.
   
   The opposite is true for objects that are at rest. In this project you will observe that an object at rest wants to stay at rest.
   
   

   Instructions for the Project:

2. Fill the mug half way with water.

3. Set the mug down in the middle of the piece of paper on a table or other flat, smooth surface. Make sure the outside of the mug and the paper are completely dry.

4. With a sharp jerk, pull the paper out from under the mug. If you have trouble keeping the mug in place, move it closer to the edge of the table. Grab hold of the paper that is hanging over the edge of the table, hold it straight out, and quickly strike the paper with a downward blow using a ruler. Why does the mug stay on the table?

5. Try pulling the paper out from under the mug using a variety of motions and forces.

6. Record your observations.

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