Newton’s 2nd Law of Motion

By: Heather Britton

Newton’s 2nd Law of Motion

• Newton’s 2nd Law of Motion states...

• The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. The direction of the acceleration is the direction of the net force acting on the object

Newton’s 2nd Law of Motion

• Or more simply stated

• ΣF = ma

• Sigma (Σ) - the sum of....

• F - force measured in Newtons

• 1 Newton = 1 kgm/s2

Newton’s 2nd Law of Motion

• Matter - anything that has mass and occupies space

• Mass - the measure of the amount of matter on object contains

• It is also the measure of the inertia a body contains

Newton’s 2nd Law of Motion

• The more inertia a body contains the harder to change its state of motion

• The SI unit for mass (m) is the kilogram (kg)

• Mass is not the same as weight

Newton’s 2nd Law of Motion

• A body’s mass does not change depending on location

• Weight is a force and is gravity dependent

• Weight can change as a gravitational field changes

Newton’s 2nd Law of Motion

• Weight is mass multiplied by the acceleration of gravity

• Since the moon has only about 1/6 the gravity of Earth you would weigh 1/6 of your Earth weight on the moon

• However, your mass would not change

Newton’s 2nd Law of Motion

• There can be many different types of forces including

• Fg - force of gravity or weight

• FT - force caused by tension

• Ff - forces caused by friction

Newton’s 2nd Law of Motion

• Example 1

• What net force is required to accelerate a 1500 kg race car at 3.0 m/s2?

Newton’s 2nd Law of Motion

• Example 2

• An artillery shell has a mass of 55 kg. It leaves a 1.5 m gun barrel with a velocity of 770 m/s. What is the force on the shell while it is in the gun barrel?