Download Unit 4 – Force and the Laws of Motion

Unit 3 – Force and the Laws of Motion
Objectives
By the end of this unit, you should be able to do the following:
1. Describe and give examples of Newton's 1st Law.
Newton's 1st Law: Objects at rest stay at rest, objects in motion stay in motion at
constant speed in a straight line unless acted upon by unbalanced forces.
2. Given a diagram or a written description of the forces acting on an object:
a. draw and label a force diagram for the object
b. choose the simplest coordinate axis for analysis: horizontal-vertical or parallelperpendicular
c. break forces into x and y components using trigonometry.
d. state whether the velocity of the object is constant or changing.
3. Understand and apply Newton's 3rd Law. Recognize that all forces come in pairs;
paired forces are equal in magnitude, but opposite in direction. FAB = -FBA
Newton's 3rd Law: For every force, there is an equal and opposite force. Another way
of thinking about Newton's third law: You can't touch without being touched and you can
only touch as hard as you are touched.
4. Understand and apply Newton's 2nd Law: The acceleration of an object is directly
proportional to the net force on an object and inversely proportional to the mass of the
object (a = ΣF/m or ΣF = ma).
5. Use Newton's 2nd Law to qualitatively describe the relationship between m and a, F
and a, m and F. (For example, if you double the mass, the acceleration will . . ?)
6. Solve quantitative problems involving forces, mass and acceleration using Newton's
2nd Law.
a. use force diagram analysis in order to determine the equation for the forces acting
on an object in a particular direction.
b. Use Newton's second law to determine an object's acceleration and/or missing
force.
c. Use kinematics to determine the acceleration needed to be used in Newton’s
second law. Use Newton’s second law to determine the acceleration needed in a
kinematic calculation.
d. Interpret graphs of position-time, velocity-time, acceleration-time and relate them
to the net force acting on the object and vice-versa
e. Use derivatives and integrals to for part c when the acceleration is not constant.
7.
Apply the model of static friction to an object at rest (or on the verge of moving)
in order to determine the maximum static friction force or coefficient of static
friction for two surfaces.
8. Apply the model of kinetic friction to an object moving at constant speed or
accelerating in order to determine the kinetic friction force or coefficient of kinetic
friction of two surfaces.
9. Distinguish between static and kinetic friction and qualitatively describe what factors
affect it.
10. Distinguish between the mass of an object and the force of gravity acting on it, aka
weight.
11. Recognize that forces are classified as either contact and non-contact forces. Also,
be able to distinguish which of the four fundamental forces a particular force is.
12. For an object moving where drag is a factor:
a. Draw the graphs of y vs. t, v vs. t, and a vs. t and understand the basic features
of the graph
b. Determine the terminal velocity of the object recognizing that the acceleration
is zero
c. Express Newton’s second law in differential form
Text Reference
Chapters 4 & 5