1. Newton’s 2 nd Law of Motion

2. 2 nd Law Defined The acceleration of an object depends on the mass of the object and the amount of force applied The acceleration of an object depends on the mass of the object and the amount of force applied Describes the motion of an object when an unbalanced force acts on the object Describes the motion of an object when an unbalanced force acts on the object

3. Acceleration Depends on Mass The acceleration of an object decreases as its mass increases The acceleration of an object decreases as its mass increases The acceleration of an object increases as its mass decreases The acceleration of an object increases as its mass decreases

4. Example Suppose you are pushing an empty cart. You have to exert only a small force on the cart to accelerate it. But, the same amount of force will not accelerate the full cart as much as the empty cart. Suppose you are pushing an empty cart. You have to exert only a small force on the cart to accelerate it. But, the same amount of force will not accelerate the full cart as much as the empty cart.

5. Acceleration Depends on Force An object’s acceleration increases as the force on the object increases. An object’s acceleration increases as the force on the object increases. An object’s acceleration decreases as the force on the object decreases. An object’s acceleration decreases as the force on the object decreases. The acceleration of an object is always in the same direction as the force applied. The acceleration of an object is always in the same direction as the force applied.

6. Example Suppose you give the cart a hard push. The cart will start moving faster than if you gave it only a soft push. The cart will move forward because the push was in the forward direction. Suppose you give the cart a hard push. The cart will start moving faster than if you gave it only a soft push. The cart will move forward because the push was in the forward direction.

7. Expressing 2 nd Law Mathematically The relationship of acceleration (a) to mass (m) and force (F) can be expressed mathematically: The relationship of acceleration (a) to mass (m) and force (F) can be expressed mathematically: a = F/m a = F/m F = m x a F = m x a m = F/a m = F/a

8. Example What is the acceleration of a 3 kg mass if a force of 14.4 N is used to move the mass? What is the acceleration of a 3 kg mass if a force of 14.4 N is used to move the mass? (Note: 1 N is equal to 1 kg x m/s 2 ) (Note: 1 N is equal to 1 kg x m/s 2 )