Newton’s 2nd Law of Motion

Force & Acceleration

Newton’s 1st Law

• An object in motion will stay in motion and an object at rest will stay at rest if the net force is…

Newton’s 1st Law

• AKA the Law of Inertia

• Objects with lots of mass have lots of inertia. They resist motion.

• Therefore, an increase in mass results in a(n) decrease in acceleration.

• Acceleration and mass are said to be inversely proportional.

Apply an equal Force to each…

Force and Acceleration

The more force applied, the greater the acceleration. That is because force and acceleration are directly proportional.

Who will be able to

throw the soccer ball

further?

Newton’s 2nd Law of Motion

The amount of force applied to an object is equal to its mass times its acceleration.

F = m * a

-F is force, measured in Newtons (N)

-m is mass, measured in kilograms (kg)

-a is acceleration, measured in meters per second per second (m/s/s)

F = m*a

• The equation can be rearranged for acceleration:

– To calculate the acceleration an object undergoes…

Newton’s 2nd Law

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

• Think free fall motion…

..the acceleration was in

the downward direction

because gravity was

pulling an object down.

Example Math Problem

• A car has a mass of 1000 kg. What is the acceleration produced by a force of 2000 N?

How much force?

• How much force, or thrust, must a 30,000 kg jet plane develop to achieve an acceleration of 1.5 m/s2?

Free Body Diagram

• A diagram showing all the forces acting on an object.

• Force is a

vector

quantity.

Force Problems

• Johnny has a mass of 100 kg. What is his acceleration if a force of 100 N is applied?

• Johnny is resisted by 50 N of friction. What is his acceleration?