LAB 6: SPRING CONSTANT AND ENERGY

A mass attached to a vertical spring will come to equilibrium when the force of the spring acting on the mss is equal to the weight of the mass. The displacement caused by the mass is proportional to the force of the spring on the mass. The proportionality constant for this relation ship is called the spring constant, k.

If the mass is given an initial displacement from its equilibrium position, it will oscillate vertically. At the top of the oscillation, the spring has maximum gravitational potential energy. At the bottom of the oscillation, the spring has maximum elastic potential energy

In this experiment we will compare these two forms of potential energy as a test of the law of conservation of energy.

OBJECTIVES:

1. Find the spring constant.

1. Verify the law of. Conservation of energy in an oscillating spring.

MATERIALS:

1. Hooke's law apparatus
2. Set of masses

1. Set up the apparatus and calibrate the pointer by adjusting the scale so that the pointer is at zero when there is no mass attached to the spring.
2. Hang a mass on the pan and let it down slowly until it reaches an equilibrium position. Record the displacement and the mass.
3. Pull the mass down to give it a displacement and record the position. Release it and record the positions of the highest point the mass reaches.
4. Repeat steps 2 and 3 for trials 2 through 5 using various masses.

DATA TABLE: prepare by the day of the lab.

CALCULATIONS: Do the following calculations for each of the five trials and record them on the result table.

1. Find the spring constant for each trial
2. Use the spring constant for each trial to calculate the elastic potential energy loss from the lowest position to the highest position.
3. Calculate the change in the gravitational potential energy from the lowest position to the highest position.
4. Calculate for each trial the per cent difference between the changes in elastic and gravitational potential energy, which is the difference, divided by the average of the two energies.
5. Calculate the average spring constant for the 5 trials.
6. Use a graph of force versus displacement to find the average spring constant for the 5 trials.
7. Find the per cent difference between the values for the spring constant from part 5 and part 6.

SAMPLE CALCULATIONS:

RESULTS TABLE:

1. What type of graph would you expect for part 6 and why?
2. From the graph in part 6, how were you able to find the spring constant? Explain why.
3. What does the spring constant tell you about the spring itself?
4. What is your result from part 4? What does this show?

CONCLUSION: Summarize your findings and thoughts about lab.