1. 6.2 Newton's Second Law pp. 142-146

2. NEWTON’S SECOND LAW OF MOTION The acceleration of an object depends on the mass of the object and the amount of force applied to it. The acceleration of an object depends on the mass of the object and the amount of force applied to it.

3. NEWTON’S SECOND LAW OF MOTION In other words… In other words… Force causes an object to accelerate, while the object’s mass resists the acceleration. Force causes an object to accelerate, while the object’s mass resists the acceleration. The larger the object (the more mass it has), the harder it is to accelerate. The larger the object (the more mass it has), the harder it is to accelerate.

4. 6.2 The newton The S.I. unit of force (newton) is defined by the second law. The S.I. unit of force (newton) is defined by the second law. A newton is the amount of force needed to accelerate a 1 kg object by 1m/s/s. A newton is the amount of force needed to accelerate a 1 kg object by 1m/s/s.

5. Measuring Force There are 2 units that are commonly used to measure force: There are 2 units that are commonly used to measure force: Pounds Pounds Newtons Newtons 1Newton = 1 kilogram m/sec 2 1Newton = 1 kilogram m/sec 2 1pound = 4.448 Newtons 1pound = 4.448 Newtons 1 Newton isn't a very big force: it's about the weight of an apple 1 Newton isn't a very big force: it's about the weight of an apple

6. 6.2 Newton’s second law There are three main ideas related to Newton’s Second Law: There are three main ideas related to Newton’s Second Law: 1. Acceleration is the result of unbalanced forces. 2. A larger force makes a proportionally larger acceleration. 3. Acceleration is inversely proportional to mass.

7. 6.2 Newton’s second law Unbalanced forces cause changes in speed, direction, or both. Unbalanced forces cause changes in speed, direction, or both.

8. 6.2 Acceleration, force and mass The acceleration caused by a force is proportional to force and inversely proportional to mass. The acceleration caused by a force is proportional to force and inversely proportional to mass.

9. 6.2 Applying the second law Keep the following important ideas in mind: Keep the following important ideas in mind: 1. The net force is what causes acceleration. 2. If there is no acceleration, the net force must be zero. 3. If there is acceleration, there must also be a net force. 4. The force unit of newtons is based on kilograms, meters, and seconds.