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The activity described below gets everyone’s attention! Students with a visual impairment benefit from a chance to feel the weight of the various items placed on the tablecloth, as well as a chance to examine the table before and after the table cloth is pulled.

### Vocabulary

Inertia – the tendency of an object to keep its motion

### Inertia

Place a book on your desk. Does the book move? Unless you push the book, it will stay put just the way you left it. Imagine a spacecraft moving through space. When the engines are turned off the spacecraft will coast through space at the same speed and in the same direction. The book and spacecraft have inertia. Because of inertia, an object at rest rends to stay at rest. An object in motion tends to keep moving at a constant speed in a straight line.

### Newton's First Law

Newton’s first law of motion explains how inertia affects moving and nonmoving objects. Newton’s first law states that an object will remain at rest or move at a constant speed in a straight line unless it is acted on by an unbalanced force. According to Newton’s first law, an unbalanced force is needed to move the book on your desk. You could supply the force by pushing the book. An unbalanced force is needed to change the speed or direction of the spacecraft. This force could be supplied by the spacecraft’s engine.

### Effects of Interia

You can see the effects of inertia everywhere. In baseball, for example, to overcome inertia a base runner has to “round” the bases instead of making sharp turns. As a more familiar example of inertia, think about riding in a car. You and the car have inertia. If the car comes to a sudden stop, your body tends to keep moving forward. When the car starts moving again, your body tends to stay at rest. You move forward because the car seat exerts an unbalanced force on your body.