2. 2.4: Newton’s Second Law of Motion

3. What if... If you kept increasing the amount of applied force on an object, would its acceleration increase or decrease? If kept the applied force constant but increased the object’s mass, would its acceleration increase or decrease? Consider the following: a) race carb) semi-trailerc) smart car

4. Newton’s Second Law of Motion An object accelerates in the direction of the net force. The magnitude of an object’s acceleration is directly proportional to the net force acting on it and is inversely proportional to its mass. ma F net

5. Does Newton’s Second Law agree with the First Law? Second Law: F net = ma If F net = 0, then a must also be zero. The object must be either at rest or moving at constant velocity. Therefore, the laws are consistent.

6. Example 1 A water polo ball of mass 0.45 kg accelerates at a rate of 130 m/s 2 [W]. Calculate the applied force.

7. Example 2 In an extreme test of its braking system under ideal conditions, a Honda CR-Z, travelling initially at 26.9 m/s [S], comes to a stop in 2.61 s. The mass of the car, with the driver, is 1.44 x 10 3 kg. Calculate a)the car’s acceleration

8. Example 2, cont’d b) the net force required to cause that acceleration.

9. Homework Pg. 133 #1-6 Pg. 136 #1-6,11