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Physics Essential Standards Covered:
Physics Essential Standards Covered:
Phy.1.2.1
From a free body diagram, assess the interdependence of vector components of forces; resolve forces into perpendicular components.
Apply Newton’s second law as the sum of all forces in a given direction so that the net force acting on an object in static equilibrium is zero and in a dynamic situation equal to ma.
Phy.1.2.2
Analyze systems of forces involving objects at rest (on a surface or suspended), objects pulled or pushed along a horizontal surface by an applied force that is either parallel to the surface or applied at an angle, objects sliding or rolling down an inclined plane.
Distinguish forces on objects based on interactions including contact and forces at a distance (normal force, weight, friction, tension, applied force).
Key Vocabulary
Key Vocabulary
Force
Non-contact Force
Contact Force
Magnitude
Direction
Vector
Gravitational Force
Electromagnetic Force
Weak Nuclear Force
Strong Nuclear Force
Applied Force
Weight
Normal Force
Net Force
Frictional Force
Tension Force
Air Resistance Force
Buoyancy Force
Spring Force
Lift
Essential Question: What is force, and how is it used to describe motion?
Essential Question: What is force, and how is it used to describe motion?
Lesson:
Lesson:
We are going to forget everything we learned using Kinematics and actually care about the different forces that act on objects as they move.
We are going to forget everything we learned using Kinematics and actually care about the different forces that act on objects as they move.
4 Major Forces of Nature (non-contact force):
4 Major Forces of Nature (non-contact force):
- Gravitational Force: The force due to the gravitation acceleration of large bodies in space.
- Electromagnetic Force: The force due to the attraction between charged particles and magnets.
- Weak Nuclear Force: The force responsible for radioactive decay within an atom and how the particles within the atom interact with one another.
- Strong Nuclear Force: The force that holds the nucleus of an atom together.
Strong Force > Weak Force > Electromagnetic Force > Gravitational Force
Strong Force > Weak Force > Electromagnetic Force > Gravitational Force
We will mostly focus on the gravitational force and the electromagnetic force in this class.
We will mostly focus on the gravitational force and the electromagnetic force in this class.
Contact Forces:
Contact Forces:
- Where a force is applied by an outside source (a push or a pull).
Types of contact forces:
Types of contact forces:
- Friction
- Tension
- Air resistance
- Buoyancy
- Spring
- Lift
- Drag
- Normal Force
Units for Force:
Units for Force:
- Newtons!
- N
- kg m/s^2
Force is a vector quantity: Magnitude and Direction Matters!
Force is a vector quantity: Magnitude and Direction Matters!
To find the force in the x and y planes we find the sum of the forces.
To find the force in the x and y planes we find the sum of the forces.
The sum of the forces is also known as the Net Force
The sum of the forces is also known as the Net Force
How do we make sense of all these vectors? Especially if we have a lot of of forces acting on an object?
How do we make sense of all these vectors? Especially if we have a lot of of forces acting on an object?
- Free body diagrams
- We draw a picture
- Add the force vectors in the direction the force is applied
- Label the forces.
Forces that will always exist in your free body diagram:
Forces that will always exist in your free body diagram:
- Gravitational force vector pointing down ward.
- Normal Force vector pointing upwards.
- The normal force is the support force exerted upon an object that is in contact with another stable object.
Important to remember: The net force and gravitational force are always equal and opposite to each other. This is why you don't fall through you chair when you are sitting. The normal force is holding you up! (we will learn more about this when we learn about Newton's laws).
Important to remember: The net force and gravitational force are always equal and opposite to each other. This is why you don't fall through you chair when you are sitting. The normal force is holding you up! (we will learn more about this when we learn about Newton's laws).
Examples:
Examples:
- A book is pushed across a friction-less surface with a force of 12 Newtons. Draw a free body diagram for this situation. Calculate the net force.
- You are sitting in a chair and are stationary, draw a free body diagram for this situation. Calculate the net force
- We decide to have an epic tug of war contest for our physics class. We tug and tug and tug on both sides but no one moves because we are equally pulling with a force of 5 N on each side. Draw a free body diagram depicting this scenario. Finally someone gets some muscles and starts pulling harder on the right side with a force of 7 N. Draw a free body depicting this new scenario. Calculate the net force for both scenarios.
Newton's Three Law's of Motion:
Newton's Three Law's of Motion:
- Inertia: An object in motion will stay in motion, or an object at rest will stay at rest unless acted on by an external force.
2. F = ma: If you apply a force to an object that has a mass, that object will accelerate.
2. F = ma: If you apply a force to an object that has a mass, that object will accelerate.
3. Equal and Opposite: For every action there is an equal and opposite reaction.
3. Equal and Opposite: For every action there is an equal and opposite reaction.
Answer essential question In notebook 3-5 sentences: What is force, and how is it used to describe motion?
Answer essential question In notebook 3-5 sentences: What is force, and how is it used to describe motion?
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