1. Chapter 6 NEWTON’S 2 ND LAW Unbalanced Force Causes Acceleration

2. Newton’s 2 nd Law Unbalanced force means a net force greater than zero F net > 0 The acceleration of an object is directly proportional to and in the same direction as the unbalanced force causing it Acceleration is inversely proportional to the mass of the object

3. Formulas a ~ F a ~ 1/m a = F /m or F = ma Acceleration in m/s 2 Mass in kilograms (kg) Force in Newtons (N) N = kg m /s 2

4. Examples of Forces Mechanical push or pull Gravity Friction Electric Magnetic Nuclear

5. Friction Friction is a force that opposes motion Negative force Causes deceleration Generates heat (energy lost from system) Rolling friction is less than sliding friction

6. Weight & Falling Weight is force Weight is a product of mass and the acceleration of gravity F g = m g g = 10 m/s 2 (Earth) Weight is measured in Newtons (N) 4.5N = 1 lb When falling through the air weight pulls down but air drag pushes up Net force is difference between weight and drag If weight = drag acceleration is zero (terminal velocity )

7. Pressure Pressure is force over an area Pressure = Force / Area (P = F/A) Measured in Newtons / square meter (N/m 2 = pascal) Pounds / square inch (psi)