Review test, introduction to dynamic forces Thursday, September 22, 2016

Unit 3: Dynamic Forces Thursday, 9/22 Analyze the photo to the right and respond to the following: How does the mass, velocity, displacement, and time passage, of the object (diver) change from the top of the cliff to the bottom? Upcoming important dates Thursday, 9/22 – homework quiz Monday, 9/26 – homework quiz Wednesday, 9/28 – homework quiz Friday, 9/30 – Newton’s 2nd and 3rd law quiz Tuesday, 10/4 – Friction quiz Thursday, 10/6 – homework quiz Tuesday, 10/11 – unit quiz Thursday, 10/13 – unit test (note grade goes on 2NWS) Image source: https://upload.wikimedia.org/wikipedia/ commons/5/59/Acapulco_Cliff_Diver.jpg

Review Test Pick up test and a sticky note. If you have questions about your test, write it on a sticky note and place it on your test.

Unit 3: Dynamic Forces Thursday, 9/22 Analyze the photo to the right and respond to the following: How does the mass, velocity, displacement, and time passage, of the object (diver) change from the top of the cliff to the bottom? Image source: https://upload.wikimedia.org/wikipedia/ commons/5/59/Acapulco_Cliff_Diver.jpg

Where we’ve been… Inertia (Newton’s first law of motion) applies when forces are balanced. Object is at rest Object is moving at a constant velocity We’ve used vectors, FBDs, and Net Force equations to analyze objects which have balanced forces

Where we are going… Analyzing objects with unbalanced forces! Viewing unbalanced forces through multiple lenses; acceleration, momentum, energy.

Unbalanced Forces Result in a change in velocity meaning the object is accelerating. Results in a net force greater than zero Example: The object represented in the FBD has a mass = 6 kg. Calculate the weight of the object. Calculate the net force

Acceleration - magnitude Final velocity, m/s Initial velocity, m/s Change in time, s

Acceleration a =ΣF m Units: m/s2

Acceleration magnitude and direction An 800-kg car is coasting to the right with a leftward acceleration of 1 m/s2. Diagram the forces acting upon the car.

An 800-kg car is coasting to the right with a leftward acceleration of 1 m/s2. Diagram the forces acting upon the car. Big idea: an object can be accelerating in one direction and moving in a different direction.

Newton’s 2nd Unbalanced forces cause a change in the motion of the object. The amount of change is dependent on the magnitude of the force and the mass. larger force = larger change in motion larger mass = small change in motion Amount of change can be expressed in three different ways.

Newton’s 2nd Law of motion expressions Acceleration Momentum Kinetic Energy a =ΣF m Units: m/s2 Relationships: p = mv Δp = ΣFΔt Units: kg * m s Relationships: K = ½mv2 ∆K =ΣF∙d Units: N*m or Joule (J) Relationships:

Momentum When watching the video do the following: What systems are acting on the puck? What determines the acceleration of the puck when it makes contact with the stick? How was the term energy used? http://www.nbclearn.com/portal/site/learn/search

Energy When watching the simulation analyze the following: The relationship between velocity and kinetic energy for the roller coaster car (Ex: does it change, if does change what is the contributing variable to the change? http://www.physicsclassroom.com/mmedia/energy/ce.cfm

Newton’s 2nd Law of motion expressions Acceleration Momentum Kinetic Energy a =ΣF m Units: m/s2 Relationships: p = mv Δp = ΣFΔt Units: kg * m s Relationships: K = ½mv2 ∆K =ΣF∙d ∆K = Kf - Ki Units: N*m or Joule (J) Relationships:

G: Momentum a =ΣF m ∆K =ΣF∙d K = ½mv2 ∆K = Kf - Ki A net force of 50 N is exerted on a 25 kg object for 4s, during which time the object started from rest and moved forward 16 meters. Calculate: G: Acceleration Momentum Kinetic Energy a =ΣF m p = mv Δp = ΣFΔt ∆K =ΣF∙d K = ½mv2 ∆K = Kf - Ki

Home work review – 20 minutes With a partner, work through homework assignment