1. Ch. 6 – Newton’s 2 nd Law of Motion – Force & Acceleration I. Review of Previous Information A. Changes in motion (acceleration) are caused bya force!! (or The Force ) B. Net Force = 0 =Balanced Forces =No acceleration!! C. Net Force not 0 =Non-Balanced Forces =Acceleration!!

2. II. Newton’s 2 nd Law of Motion A. The amount of force on an object affects its acceleration B. The amount of mass of an object also affects its acceleration C. So… lesser masses and greater forces cause larger accelerations! [Directly Prop.] [Inversely Prop.] 1. Makes sense says Newton, let’s make it a law!! 2. In equation form  a = F/m (SI units = m/s 2 )

3. III. Falling objects A. Without air resistance…all objects fall at the same rate(9.8 m/s 2 ) B. With air resistance… Objects fall at different rates and change accelerations 1.Higher speeds and larger shape lead to higher forces due to increased air resistance 2. When weight and the force from air resistance are equal, net force = 0,acceleration = 0,velocity is constant(Terminal Velocity) 3. What happens between 0 velocity and terminal velocity?

4. Practice Problems Human Cannonball! Weighs 180 pounds and is shot with a Force of 1600 N. a = ? Human Cannonball! Weighs 180 pounds and is shot with a Force of 1600 N. a = ? First, 180 lbs into kg…(2.2 lbs = 1 kg) First, 180 lbs into kg…(2.2 lbs = 1 kg) Mass of 81.8 kg Mass of 81.8 kg F = ma rearranges into a = F/m F = ma rearranges into a = F/m 1600 N / 81.8 kg = a 1600 N / 81.8 kg = a Acceleration = 19.6 m/s 2 Acceleration = 19.6 m/s 2

5. Practice Problems Continued To time travel a car must accelerate at a rate of 18 m/s 2. How much Force would be required to accelerate a 1400 pound vehicle and 150 pound driver at this rate? To time travel a car must accelerate at a rate of 18 m/s 2. How much Force would be required to accelerate a 1400 pound vehicle and 150 pound driver at this rate? First convert pounds into kilograms First convert pounds into kilograms 1550 pounds (car and driver) = 704.5 kg 1550 pounds (car and driver) = 704.5 kg F = ma F = ma F = 704.5 kg x 18 m/s 2 F = 704.5 kg x 18 m/s 2 F = 12,681.8 N F = 12,681.8 N The engine would have to exert a force of at least 12,681.8 N to achieve time travel! The engine would have to exert a force of at least 12,681.8 N to achieve time travel!