Newton’s 2Newton’s 2ndnd Law of MotionLaw of Motion

22ndnd Law Defined Law Defined The acceleration of an object The acceleration of an object

depends on the mass of the depends on the mass of the object and the amount of force object and the amount of force appliedapplied

Describes the motion of an object Describes the motion of an object when an unbalanced force acts on when an unbalanced force acts on the objectthe object

Acceleration Depends on MassAcceleration Depends on Mass

The acceleration of an object The acceleration of an object decreases as its mass decreases as its mass increasesincreases

The acceleration of an object The acceleration of an object increases as its mass increases as its mass decreasesdecreases

ExampleExampleSuppose you are pushing an Suppose you are pushing an

empty cart. You have to exert empty cart. You have to exert only a small force on the cart only a small force on the cart to accelerate it. But, the to accelerate it. But, the same amount of force will not same amount of force will not accelerate the full cart as accelerate the full cart as much as the empty cart.much as the empty cart.

Acceleration Depends on ForceAcceleration Depends on Force

An object’s acceleration increases as An object’s acceleration increases as the force on the object increases.the force on the object increases.

An object’s acceleration decreases as An object’s acceleration decreases as the force on the object decreases.the force on the object decreases.

The acceleration of an object is The acceleration of an object is always in the same direction as the always in the same direction as the force applied.force applied.

ExampleExampleSuppose you give the cart a Suppose you give the cart a

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

Expressing 2Expressing 2ndnd Law Mathematically Law Mathematically

The relationship of acceleration The relationship of acceleration (a) to mass (m) and force (F) can (a) to mass (m) and force (F) can be expressed mathematically:be expressed mathematically:

a = F/ma = F/m F = m x aF = m x a m = F/am = F/a

ExampleExampleWhat is the acceleration of a What is the acceleration of a

3 kg mass if a force of 14.4 3 kg mass if a force of 14.4 N is used to move the mass? N is used to move the mass?

(Note: 1 N is equal to 1 kg x (Note: 1 N is equal to 1 kg x m/sm/s22))