Newton’s first law REVIEW Summarize what the law states. What does an object at rest need for it to move? What is another name for newton’s first law of motion? What is inertia? What causes a moving object to stop moving? The (more/less) mass an object has, the harder it is to move.

Newton’s Second Law

NEWTON’S second law The acceleration of an object depends on the mass of the object and the amount of force applied. VOLUNTEERS!!!!! TWO “pushers” of similar size ONE small 8th grader ONE big 8th grader Have the “small” and “big” student sit in a chair. Have the “pushers” push them across the room. Discuss which required more energy and why.

Part 1: Acceleration depends on mass Acceleration of an object decreases as its mass increases Acceleration of an object increases as its mass decreases Which would be easier to push? WHY?

Part 2: Acceleration depends on force Acceleration of an object increases as the force on it increases Acceleration of an object decreases as the force on it decreases VOLUNTEERS!!!!! ONE to sit in chair ONE to push chair

Newton’s law with MATH mass Force acceleration Formula: F = m a Have students guess what the variables represent UNITS  acceleration: m/s² (meters per second squared) force: N (Newtons) mass: kg (kilograms)

If you want to find Force Force = Mass X Acceleration (F= M X A), Unit is the Newton (N), Force F ÷ ÷ A M X Acceleration Mass Mass = Force ÷ Acceleration, (M = F ÷ A) Measured in kilograms (kg) Acceleration = Force ÷ Mass, Measured in meters per second squared (m/s²) Copyright © 2010 Ryan P. Murphy

Let’s Practice Complete guided practice worksheet with me, then tape in your journal.

Newton’s Laws video clip http://www.youtube.com/watch?v=nJTKiS444BQ