Physics
Constant Net Force Models
Unit 5
Unit Essential Questions
What are the causal models of motion and how are they used?
What are the graphical models and the mathematical models that are used to represent
and analyze the behavior of an object subject to a constant net force?
What is the relationship between a system’s acceleration and the system’s mass?
What is the relationship between a system’s acceleration and the net force on the system?
What is the relationship between a system’s acceleration, the system’s mass, and the net
force on the system?
What is the relationship between the normal force on an object by a surface and the
frictional force on the object by the surface?
New Enduring Understandings
A. A system’s acceleration is inversely proportional to its mass when a constant net
force is applied.
B. A system’s acceleration is directly proportional to the net force on the system.
C. A system’s acceleration is exactly equal to the quotient of net force and system mass.
D. The frictional force on an object by a surface behaves differently when the object is
sliding than when the object is at rest.
E. The frictional force on an object by a surface is directly proportional to the normal
force on the object by the surface.
F. The frictional interaction between two substances can be quantified by the frictional
coefficient.
G. The air resistance on a moving object increases with velocity.
H. Graphical models and mathematical models are used to represent, analyze, and
communicate structure and relationships in physical systems and physical
interactions.
I. A relatively small number of models can be used with great versatility for a wide
variety of physical systems and physical interactions.
Edington 1/10/05 Unit 5 Constant Net Force Objectives v7.doc
Physics
Constant Net Force Models
New Terms and Symbols
µ
apparent weight
calibration curve
derived unit
force transducer
kinetic friction
photogate pulley
static friction
terminal velocity
µk
Atwood’s machine
coefficient of kinetic
friction
dynamics
frictional coefficient
modified Atwood’s
machine
sliding friction
system
two-point calibration
Unit 5
µs
calibration
coefficient of static friction
force sensor
kinematics
Newton’s second law
Smart pulleytm
system mass
New Math Concepts
Combining mathematical models, combining constants in mathematical equations,
physical property coefficients, multivariate functions
New Technology Skills
Using photogate pulleys, using force transducers, calibration
Performance Objectives
1. You should be able to quantitatively describe - graphically, mathematically, and
verbally - the relationship between an object’s acceleration and the object’s mass when
a constant net force is applied.
2. You should be able to quantitatively describe - graphically, mathematically, and
verbally - the relationship between an object’s acceleration and the net force applied to
the object when the object’s mass is constant.
3. You should be able to quantitatively describe - graphically, mathematically, and
verbally - the relationship between a system’s acceleration, the system’s mass, and the
constant net force applied to the system.
4. Given a velocity vs. time graph describing an object’s motion, you should be able to
draw the corresponding acceleration vs. time graph and net force vs. time graph.
5. You should be able to determine the net force acting on an object by
a. drawing a force diagram for the object from a written description of the forces
acting on the object, resolving each force into x- and y-components, and finding
the vector sum of the forces.
b. analysis of the object’s kinematic behavior.
6. You should be able to use force transducers, a computer interface, and data acquisition
software to acquire force and clock reading data.
7. You should be able to graphically illustrate the changes in applied force as an object at
rest is pulled from rest to a state of constant velocity.
Edington 1/10/05 Unit 5 Constant Net Force Objectives v7.doc
Physics
Constant Net Force Models
Unit 5
8. You should quantitatively describe - graphically, mathematically, and verbally - the
relationship between the normal force on an object and the frictional force on an
object.
9. Given two of the three – normal force, frictional force, and frictional coefficient – you
should be able to calculate the missing quantity.
10. You should be able to solve complex problems involving mass, time, position,
velocity, acceleration, and forces (including friction), using the dynamics
mathematical models and the kinematics mathematical models.
11. You should be able to use all of these and your prior knowledge, skills, and
understandings to represent, analyze, and communicate structure and relationships in
physical systems and physical interactions
Edington 1/10/05 Unit 5 Constant Net Force Objectives v7.doc