NEWTONIAN MECHANICS
B. Statics and Dynamics
i. An object’s inertia is its tendency to resist a change in motion
ii. Translational Equilibrium is a state where all forces on an object are balanced; the net force is zero,
there is no acceleration, and the object’s velocity remains constant.
iii. An unbalanced force, or net force, causes an object to change its motion (to accelerate).
iv. The Normal force is the supporting force between the surfaces of any two objects; it is the result of the
repulsive electric force among the electrons on the surfaces of the two objects.
v. N’s 1st Law: All objects remain in a constant state of motion, either at rest or moving with a constant
speed in a straight line, unless they are acted on by an unbalanced (net) force.
vi. N’s 2nd Law (Original Version): The acceleration caused by an unbalanced force on an object is
directly proportional to the magnitude of, and in the same direction as the net force, and is inversely
proportional to the mass (inertia) of the object;
vii. N’s 2nd Law (modern version, v<<c): The net force on an object is equal to the rate of change of
momentum of the object.
viii. N’s 3rd Law: When one object exerts a force on a second object, the second object exerts a force on the
first object equal in magnitude and opposite in direction.
ix. Pseudo forces, such as the coriolis effect and the centrifugal effect, appear to be real when observed
from accelerated frames of reference; in actuality, they are manifestations of an object’s inertia.
Students should conceptually understand forces, so they can:
1) Recognize the most common contact forces and how they are classified according to fundamental
forces.
2) Distinguish between forces and inertial effects (“pseudo forces”)
3) Distinguish between “conservative forces” and “non-conservative forces”; describe examples of
each.
Students should understand the significance of friction, and other drag forces, so they can:
4) Apply the relationship between the coefficient of friction, normal forces, and frictional forces on a
surface.
5) For given situations and coefficients, determine the applied force or angle of incline at which an
object will start to slip
6) Determine the frictional force, or balancing applied force necessary to cause an object to be in
equilibrium.
Students should demonstrate an ability to analyze objects acted on by multiple forces in one or two dimensions
by being able to
7) Draw proportional and well-labeled free body diagrams of all real forces that act on an object,
including appropriately-drawn components of forces
8) Solve problems for objects suspended in static equilibrium by multiple strings
9) Solve problems for objects being acted on by applied forces that are not parallel to the surface
10) Solve problems featuring objects on inclined planes; with or without friction; at rest, at constant
velocity, or accelerating.
Students should understand how Newton’s First or Second Law applies to an object subject to forces such as
gravity, the pull of strings, friction, and contact forces, so they can:
11) analyze situations in which a particle remains at rest, or moves with constant velocity, under the
influence of several forces in one or two-dimensions
12) determine the acceleration of an object acted upon by multiple forces while under the influence of
multiple forces
13) determine the magnitude and direction of the net force, or of one of the forces that makes up the net
force, on an object undergoing uniform acceleration.
1. Systems of two or more objects
Students should understand Newton’s Third Law so that,
14) they can identify the force pairs and the objects on which they act, and state the magnitude and
direction of each force.
15) apply Newton’s Third Law in analyzing the force of contact between two objects that accelerate
together along a horizontal or vertical line, or between two surfaces that slide across one another.
Students should understand the interaction of object in connected systems so they can
16) Calculate the tension of strings connecting two or more objects moving vertically, either at constant
velocity or accelerating.
17) Solve problems for two objects connected by string and suspended by a frictionless pulley (Atwood
Machine-type problems)
18) Determine the acceleration of a system of objects connected by string or cable while experiencing a
combination of surface and/or contact forces.
Physics Classroom tutorials
Newton’s 1st Law http://www.physicsclassroom.com/Class/newtlaws/u2l1a.cfm
Free Body Diagrams http://www.physicsclassroom.com/Class/newtlaws/u2l2a.cfm
Newton’s 2nd Law http://www.physicsclassroom.com/Class/newtlaws/u2l3a.cfm
Newton’s 3rd Law: http://www.physicsclassroom.com/Class/newtlaws/u2l4a.cfm
Forces in 2 Dimensions: http://www.physicsclassroom.com/Class/vectors/u3l3a.cfm
Physics Classroom Problem Sets
Newton’s Laws—Overview: http://www.physicsclassroom.com/calcpad/newtlaws/
Problem Set: http://www.physicsclassroom.com/calcpad/newtlaws/problems.cfm
weight and mass: 1—4;
2nd Law basics: 5—10; Accelerations from multiple forces: 11—30
Forces in 2 Dimensions—Overview: http://www.physicsclassroom.com/calcpad/vecforce/
Problem Set: http://www.physicsclassroom.com/calcpad/vecforce/problems.cfm
Vector addition and resolution: 1—5; Objects pulled at an angle: 6—12;
hanging tension: 13—20; motion along inclines: 21—27
Kahn Academy Links
1. Balanced and Unbalanced forces (2):
https://www.khanacademy.org/science/physics/forces-newtons-laws/balanced-unbalanced-forces/v/balanced-and-unbalanced-forces
2. Newton’s Laws (8):
https://www.khanacademy.org/science/physics/forces-newtons-laws/newtons-laws-of-motion/v/newton-s-1st-law-of-motion
3. Normal and Contact forces (2):
https://www.khanacademy.org/science/physics/forces-newtons-laws/normal-contact-force/v/normal-force-and-contact-force
4. Inclined plane and friction (6):
https://www.khanacademy.org/science/physics/forces-newtons-laws/inclined-planes-friction/v/inclined-plane-force-components
5. Tension (3):
https://www.khanacademy.org/science/physics/forces-newtons-laws/tension-tutorial/v/introduction-to-tension
Internet Archive Links
Newton’s 1st Law: http://archive.org/details/AP_Physics_B_Lesson_03/container.html
Newton’s 2nd Law: http://archive.org/details/AP_Physics_B_Lesson_04/container.html
Newton’s 3rd Law: http://archive.org/details/AP_Physics_B_Lesson_05/container.html
Applications of Newton’s Laws: http://archive.org/details/AP_Physics_B_Lesson_06/container.html
Simulations Links
Friction (kinetic model) http://phet.colorado.edu/en/simulation/friction
Static and Kinetic Friction (Forces 1-D) http://phet.colorado.edu/en/simulation/forces-1d
Forces and Motion http://phet.colorado.edu/en/simulation/forces-and-motion
The Ramp http://phet.colorado.edu/en/simulation/the-ramp
Inclined Plane http://www.walter-fendt.de/ph14e/inclplane.htm
Free Body Diagram on incline: http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1.0
2 body, table & pulley system: http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=3.0