Newtonian Mechanics Unit 3
Topic(s): Hooke’s Law
Learning Goals
- Construct Free Body Diagrams to accurately represent the Forces acting
on an object
- Identify and Explain the conditions of equilibrium in terms of Newton’s First
Law of Motion
- Experiment with a variety of equilibrium situations
Solve problems involving 1-D and 2-D Equilibrium for specific forces
and/or physical constants
HOOKE’S LAW
The Parts of Hooke’s Law
FS is the restoring spring force [N]
k is the spring constant [N/m]
x is displacement from equilibrium
(unstretched) position [m]
The negative sign is directional so that the force points the correct
way (back to equilibrium position). Oftentimes we can ignore the
negative sign
Relationship between F
and x
There is a direct relationship between Spring
force and the distance stretched
Direct relationships, when graphed, are linear
F=kx follows the format of y=mx+b
A material obeys Hooke’s Law if its graph of
Force vs. distance is linear.
Set up an FBD and
calculate “k”
A mass of 2.3kg
stretches the spring a
distance of 0.12m.
Calculate k.
Spring Constant
Misconception
The spring constant is constant for a given spring.
Different springs will have their own constants based
on the metal used to make the spring (think spring in a
pen vs. spring used in shock absorbers for a car)
A material obeys Hooke’s Law if the ratio of applied
force to distance stretched/compressed is a constant.
This constant value is the spring constant for that
material.