Starter
1. What is the spring constant for this spring?
2. What is the meaning of the y-intercept?
9
8
7
6
5
Force (N)
4
3
F = 0.5023x + 1.9818
2
1
0
0
2
4
6
8
stretch (m)
10
12
14
Starter Hooke’s Law
If a 1kg mass stretches a spring 2.5cm, what mass would stretch it
10cm?
Hooke’s Law for Springs
The force required to stretch a spring is directly
proportional to how much it is stretched, or :
F = kx
F = stretching force in Newtons
x= stretch in meters
k = the spring constant in N/m
Example
When a 10N mass is hung on a spring, it stretches .25m.
1. What is the spring constant?
k = F/x = 10/.25 = 40.0 N/m
2. How much would a 20N mass stretch the spring?
x = F/k = 20/40 = .50m
Hooke’s Law
F =kx
If you plot the stretching force on the y axis,
and the amount of stretch on the x axis, what
will the plot look like?
9
What does the slope
represent?
8
7
6
Force 5
(N) 4
Slope = k
3
2
1
0
0
5
10
stretch (m)
15
Practice - Hooke’s Law
m (kg)
x(m)
F (N)
0.00
0.00
0.00
.050
.045
.441
0.100 0.090
.980
P
Elastic Forces - Hooke’s Law
F = kx
k = 10.9 N/m
Application - Springs
Design an experiment to determine the spring constant
for:
 1 of the color coded springs
 A rubber band
Make a F vs. x graph for each with 5 data points.
Show a best fit line and determine the equation and k.
A
Open “ Hooke’s Law” loggerpro file on the K drive.
Procedure
1. Put the force sensor on the stand.
2. Put the spring on the sensor.
3. Put a weight hanger on the spring with enough
mass to open the spring up.
4. ZERO THE FORCE SENSOR.
5. The bottom of the hanger is now at the
starting position.
6. Add some weight and see how much the spring
stretches from the starting position.
7. Record the weight and the stretch.
8. Repeat with more weight.
Remember you are always measuring the stretch
from the original starting position.
9. After 5 data points, plot F vs. x and get the
slope. That is your k value.
10. Repeat for the rubber band.
Question
Did the rubber band obey Hooke’s Law? Explain
with reference to your graph.
Lab Report Checklist
1.Starter
2.Data Tables (2)
3.Sketch F vs. x Graphs (2) with slopes
4.Experimental k value for spring (1)
5.Question
6.Connection
7.Summary
Connection
What real life applications of Hooke’s Law
have you observed?
C
EXIT
Summarize your experiment including the objective,
the procedure, the results, and reasons for error.
E