1. Newton’s Second Law: Force, Mass, and Acceleration Sections 3.2-3.5

2. Acceleration and Force Anything that accelerates is acted on by a force. A force is a push or pull on an object. Acceleration is caused by applying force. Examples: Hitting a bag Steady pull of gravity

3. Force Causes Acceleration When there is a net force on an object, it produces acceleration. Acceleration also depends on something else. Can you think of what that is?

4. The Effect of Mass What happens when you kick a tin can? It accelerates (changes motion) Now what happens when you kick the same can full of rocks? Ouch! And it doesn’t accelerate as much

5. Inertia The full can has more inertia than the empty can because it has more mass. The greater an object’s mass, the greater its inertia. This also means that the greater the mass, the greater the force needed for acceleration.

6. What is Mass? Mass is not volume or weight. Mass is the amount of matter an object has Volume is a measure space Weight is the force due to gravity that acts on an object’s mass Your weight is different on the moon that it is here, but your mass is the same.

7. Mass and Acceleration Recall that the more massive an object is, the more inertia it has. Therefore, more massive objects are harder to accelerate. Acceleration is inversely proportional to mass. This means that when one gets bigger, the other one gets smaller.

8. Concept Check Suppose you apply the same amount of force to two carts, one cart with a mass of 4 kg, and the other with a mass of 8 kg. Which car will accelerate more? The 4 kg car How much greater will the acceleration be? Acceleration will be twice as much

9. Newton’s Second Law of Motion Isaac Newton was the first to realize the connection between force and mass in producing acceleration. His 2 nd Law of Motion is one of the most important rules of nature ever proposed.

10. Newton’s Second Law of Motion It links force, mass, and acceleration. Stated: The acceleration produced by a net force on an object is directly proportional to the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object.

11. Equation Acceleration = net force mass a = _F_ m This means acceleration equals the net force divided by the mass.

12. Practice Problem Consider a 1000-kg car pulled by a cable with 2000 N of force. What will be the acceleration of the car? F = 2000 N, m= 1000 kg, a= ? a = F/m a = 2000 N/1000 kg a = 2 m/s 2