Sir Isaac Newton’s Law 15 February 2016

Newton’s First Law An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

In Simple Language This means that there is a natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion.

Newton’s Second Law Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).

In Simple Language Everyone unconsciously knows the Second Law. Everyone knows that heavier objects require more force to move the same distance as lighter objects.

Newton’s Second Law Equation Second Law gives us an exact relationship between force, mass, and acceleration. It can be expressed as a mathematical equation: or FORCE = MASS times ACCELERATION

Example Mike's car, with a mass of 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s 2. Using Newton's Second Law, you can compute how much force Mike is applying to the car. Answer = 50 Newtons

Newton’s Third law For every action there is an equal and opposite re-action.

In Simple Language This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard.

Illustrations

Illustration

Students will write a letter to a 7th grader explaining why s/he can push an empty cart faster than a full cart. Draw 2-FBD (full and empty) Words and phrase to discuss: Force Acceleration Mass Inertia Newton’s Law of Motion