2. Joe belonces a stationary coin on the tip of his finger 20cm from the top of the table. How much work is Joe doing?

Joe is doing **zero** work on the coin.<br /><br />Here's why:<br /><br />* **Work** in physics is defined as the force applied to an object multiplied by the distance the object moves in the direction of the force. Mathematically, Work = Force x Distance x cos(theta), where theta is the angle between the force and displacement.<br /><br />* In this case, Joe is applying an upward force to counteract the force of gravity on the coin, keeping it stationary. While there is a force, the coin is *not* moving any distance.<br /><br />* Since the distance the coin moves is zero, the work done is also zero. He is *exerting* a force, and certainly *expending* energy to maintain that force, but in the physics sense, no *work* is being done on the coin itself.<br />