Week #2 Notes Monday, October 17 th Reminder: Week #2 Vocabulary and notes are Due on Friday, October 21st

Newton’s Second Law Fancy Definition: an object acted on by an unbalanced force will accelerate in the direction of the force Math Plug n Chug: Acceleration = Force / Mass Acceleration = m/s 2 Force = Newtons Mass = kilograms

Newton’s Second Law Easy Definition: If you apply a force, the object will move in the direction of the force Example: if you kick a ball forward….it will move forward.

Draw it. Use it. Love it.

Newton’s Second Law can tell you about changes in motion….using everyone’s favorite: math! Newton’s Second Law can tell you about changes in motion….using everyone’s favorite: math! Question: If a 10N force acts on a 2kg object, what acceleration does it give the object? Step #1: Write the plug n chug (formula) Step #2: Write the formula again, but replace with the actual measurements Step #3: Chug out the answer

Which 2 numbers can you plug in?

Question: If a 10N force acts on a 2kg object, what acceleration does it give the object? a = F/m a = 10N / 2kg a = 5 m/s 2

Friction There are 3 kinds: Rolling, static, and sliding

Rolling Friction When a wheel rolls over a surface The force is in the direction of the way the wheel is rolling

Bike wheel is moving forward The rolling friction is forward Would I be able to ride my bike on ice as good as on concrete?

Static Friction The friction that keeps a stationary object from moving

Why is her food not moving around on her tray? Static Friction keeps her food in place

Sliding Friction Happens when 2 surfaces slide past one another

Why is this player not moving in a straight line at a constant speed?

Acceleration Change in velocity divided by the amount of time required for the change to occur If the object changes speed, direction, or both  its accelerating Unit of measure: m/s 2

Acceleration If you calculate acceleration and the answer is positive: the object is speeding up If you calculate acceleration and the answer is negative: the object is slowing down

Calculate Acceleration Acceleration = (final speed – start speed) time

Air Resistance When molecules collide with an object and slows its motion  Example: hand out the car window  Example: parachuting  Example: walking in hurricane winds Air resistance is a type of friction ◦Will be opposite of the direction of the object Air resistance increases with speed

Weight & Mass They are not the same!

Weight Weight is the force of gravity on an object On Earth, objects fall back to Earth with the same acceleration: 9.8 m/s 2 Weight = mass x acceleration due to gravity For us its 9.8 m/s 2