1. Do Now:
1. Describe the energy conversion that takes place when a match is struck.
2. I spin a 2kg bucket of water around in a horizontal circle. The length of my arm is 0.7 meters and the bucket is travelling 11 m/s. What is the tension on my arm?

2. Aim: How can we apply conservation of energy to springs?
HW:

3. What does it mean for something to have potential?
An object has the ability to do work thanks to it’s position in space.
How does this apply to a spring?
Springs store energy when
Compressed or stretched.

4. Spring Potential Energy (PES)
This NOT the same as PEG
One might think “F x d” for a stretched spring would suffice for calculating PES. Why not?
PES = (1/2)kx2
Force changes continuously as a spring is compressed and stretched, so PES ≠ F x d

5. Spring Toy A spring toy with a mass of 0.02 kilograms has a spring
with a spring constant of
12 newtons per meter.
The toy is compressed 0.02
meter.
What height will the spring toy reach?
What happens to the PE when the
spring pops up?
What is the PE stored in the spring?
It becomes KE at first, then
as the toy goes up it
becomes gravitational PE.

6. Station Activity
Go to your station and attempt the following questions with your group. Remember energy must be conserved!

7. Station 1
The spring constant is 220 N/m. The spring compression is 2 centimeters. The mass of the toy is 6.5 grams.
A. Calculate the spring potential energy.
B. Calculate the max height of the toy.
PES = (1/2)kx2
PEs = J
PEG = mgh = J
h = 0.69 m

8. Station 2
A 0.1-kilogram apple is attached to a branch of a tree 2 meters above a spring on the ground below.
The apple falls and hits the spring, compressing it 0.1 meter from its rest position. If all of the gravitational potential energy of the apple on the tree is transferred to the spring when it is compressed, what is the spring constant of this spring?

9. Summary What is the equation for force on a spring?
How is PEG different from PES?
What is the total energy equation?
What is Mechanical Energy?