Prior to this section, we did not ask any questions about what causes the motion of objects to begin or to change. In this section, we will use Newton's second law develop a cause and effect relationship between forces and motion. Newton's second law can be stated as follows:

A representation with the words newton's second law (n.two.l) on the top. There is an equation that shows that the sum of all of the forces external to the system, acting on the system, is equal to the mass of the system multiplied by the acceleration of the center of mass of the system. This is also written in words below with the note that says that this equation contains vector and scalar quantities.

 

**NOTE: Just like kinematics, the rest of PH201 works under the point particle approximation. Thus, we will not need to worry about the center of mass yet. But in PH202, will will start to consider the physical shape of objects, requiring us to determine center of masses.

Check out this NASA video introducing the concept of Newton's Second Law

https://www.youtube.com/watch?v=WzvhuQ5RWJE

Big Ideas

Big Idea 1: Objects and systems have properties such as mass and charge. Systems may have internal structure.

Big Idea 3: The interactions of an object with other objects can be described by forces.

Big Idea 4: Interactions between systems can result in changes in those systems.

Learning Objectives

BoxSand Learning Objectives

  • Demonstrate the ability to determine the direction of the net force based off the direction of acceleration, or vice versa. More general: Be able to link the direction of two vectors that are related to each other by a scalar.
  • Understand the meaning of "net" when applied to vectors.
  • Reinforce the ability to add and subtract vectors by summing the forces acting on an object.
  • Connect the motion of an object (kinematics) with the forces acting on the object.
  • Reinforce the ability to decompose vectors into components.
  • Understand that forces are used to describe the interaction between two objects.
  • Understand that forces are used to describe the cause of the departure from the first law's equilibrium condition.

College Board Learning Objectives

Enduring Understanding and Essential Knowledge

Enduring Understanding

Essential Knowledge
   
   
   
   

Assumptions

Describe what the assumptions are and why they're important

 

Key Terms Icon Concept Map Icon

History

Physics Fun

Demonstration of how force is dispersed throughout an object: https://www.youtube.com/watch?v=XhudOIrANXs

 

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