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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
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Week #2 Notes Monday, October 17th 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/s2 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.
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
a = F/m a = 10N / 2kg a = 5 m/s2 Question: If a 10N force acts on a 2kg object, what acceleration does it give the object?
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
Would I be able to ride my bike on ice as good as on concrete? Bike wheel is moving forwardThe rolling friction is forward
Static Friction The friction that keeps a stationary object from moving
Static Friction keeps her food in place http://www.inmagine.com/tt062/tt0132042-photo Why is her food not moving around on her tray?
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/s2
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 Acceleration
Acceleration = (final speed – start speed) time Calculate Acceleration
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 Air Resistance
Weight & Mass They are not the same!
Weight is the force of gravity on an object • On Earth, objects fall back to Earth with the same acceleration: 9.8 m/s2 Weight = mass x acceleration due to gravity For us its 9.8 m/s2 Weight