Forces 09.18.12. Warm-up 1.What two factors effect the force of gravity? 2.How do balanced and...
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Transcript of Forces 09.18.12. Warm-up 1.What two factors effect the force of gravity? 2.How do balanced and...
Warm-up
1. What two factors effect the force of gravity?2. How do balanced and unbalanced forces
effect motion?
Forces (pages 21-28)Essential Questions
Finish from other day if you need to.
1. What is a force?2. What is an example of a contact and a
noncontact force?3. What two factors determine the force of
gravity?4. How does friction effect motion?5. How do balanced and unbalanced forces
effect motion?
Forces (pages 21-28)Essential Questions
1. What is a force?push or a pull
2. What is an example of a contact and a noncontact force?contact – frictionnoncontact - gravity
3. What two factors determine the force of gravity?mass and distance
4. How does friction effect motion?works in the opposite direction of motion
5. How do balanced and unbalanced forces effect motion?balanced – stationary or constant speed and directionunbalanced - acceleration
Check for Understanding• Describe how forces apply to the people in these videos.
– Jeb Corliss– Ken Block– Travis Pastrana– Remote Kontrol– Danny MacAskill
• Use four vocabulary terms in your description– Force– Noncontact– Contact– Gravity– Friction– Balanced– Unbalanced
DOL
• A car is traveling at a constant speed and direction.
1. What is a contact force acting on the car?2. What is a noncontact force acting on the car?3. How does friction effect the car?4. Are the forces balanced or unbalanced?
Explain.
Friction
1. Describe 3 areas or instances where having more friction on a bicycle is a “good thing”.
2. Describe 3 areas or instances where having more friction on a bicycle is a “not-so-good thing”?
Balanced and unbalanced forces
Notes• Balanced forces
– No motion– Constant speed in same
direction
• Unbalanced forces– Motion– Changing speed or direction
Sim Questions1. What if gravity and
buoyancy are unbalanced?2. What if gravity and
buoyancy are balanced?3. Why does weight change in
water but not mass?
Force diagram vocabulary
• Gravity – always straight down• Normal – opposes gravity, when object is
resting on a solid surface• Buoyant – opposes gravity when object is
suspended in a fluid (liquid or gas)• Applied – “push or pull”• Friction – opposes applied force
Warm-up - CopyForce diagrams
• Gravity – straight down• Normal – opposes
gravity when object is resting on a solid surface
• Applied – push or pull• Friction – opposes
applied force and motion
Aerodynamics of flight
1. What are the four forces impacting flight?2. How is lift generated?3. What is the relationship between weight and
lift?4. What is the relationship between thrust and
drag?
Formula 1…Jedi masters of aerodynamics
Force diagram problems
• A 1000 N couch is being pushed with 450 N of force to right. The friction is 500 N.
• Are the forces balanced or unbalanced?
• Will the couch move?
Applied450 N
Normal1000N
Gravity1000N
Friction500N
Warm-up
• If an object is being pushed with 200 N of force and has 250 N of static friction, will it move? Explain.
Force diagram practice1. A 20,000 N (down) plane has 10,000 N of drag (back) and 50,000
N of thrust (forward) and is able to generate 30,000 N of lift (up). Sketch a force diagram, identify the forces as balanced or unbalanced, and decide if the object is moving.
2. A piece of wood weighing 100 N in placed in a tub of water. The buoyant force on the wood is equal to 100 N. Sketch a force diagram, identify the forces as balanced or unbalanced, and decide if the object is moving.
3. How could one team beat another team in tug-of-war if both teams have the same overall weight and both teams are pulling with the same force? Sketch a force diagram to help explain your answer.
DOL1. Why must engineers consider forces when
designing different modes of transportation? Give specific examples.
2. Force diagramsa) Sketch a force diagram showing an 800 N football
player pushing a 500 N tackling dummy with 1000 N of force. The friction is 250 N.
b) Are the forces balanced or unbalanced?c) Is the tackling dummy moving?