Level 1 Physics

Vandebilt Catholic High School

W. Dupre

Lab: Conservation of Energy

EQUIPMENT NEEDED:

— Dynamics Cart with Mass (ME-9430)         — Dynamics Cart Track

— Super Pulley with Clamp                              — Meter stick

— Base and Support rod (ME-9355)               — Mass hanger and mass set

— String                                                                      (several kilograms)

— Mass balance                                              — Graph paper

Purpose

The purpose is to examine spring potential energy and gravitational potential energy and to show how energy is conserved.

 

Theory

The potential energy of a spring compressed a distance x from equilibrium is given by Us = (1/2)kx where k is the spring constant. According to Hooke’s Law, the force exerted by the spring is proportional to the distance the spring is compressed or stretched, F = kx, where k is the proportionality constant. Thus the spring constant can be experimentally determined by applying different forces to stretch or compress the spring different distances. When the force is plotted versus distance, the slope of the resulting straight line is equal to k.

 

The gravitational potential energy gained by a cart as it climbs an incline is given by Ug = mgh, where m is the mass of the cart, g is the acceleration due to gravity, and h is the vertical height the cart is raised. In terms of the distance, d, along the incline, the height is given by h = d sinq.

If energy is conserved, the potential energy in the compressed spring will be completely converted into gravitational potential energy.

 

Procedure

 

  1. Level the track by setting the carton the track to see which way it rolls. Adjust the leveling feet to raise or lower the ends until the cart placed at rest on the track will not move.
  2. Use the balance to find the mass of the cart. Record this value in your data table.
  3. To determining the spring constant (k)
    1. Set the cart on the track with the spring plunger against the stopping block as shown in  

Figure 9.1. Attach a string to the cart and attach the other end to a mass hanger, passing the string over the pulley.

    1. Record the cart’s position in Table 9.1.
    2. Add mass to the mass hanger and record the new position. Repeat this for a total of 5 different masses.

4.    Remove the string from the cart and cock the spring plunger to its maximum compression position. Place the cart against the end stop. Measure the distance the spring plunger is compressed and record this value in your data table.

5.    Incline the track and measure its height and hypotenuse (see Figure 9.2) to determine the angle of the track (sinq  = opp / hyp) . Record the angle in your data table.

6.    Record the initial position of the cart in your data table.

7.    Release the plunger by tapping it with a stick and record the distance the cart goes up the track. Repeat this five times. Record the maximum distance the cart went in your data table.

8.    Change the angle of inclination and repeat the measurements.

9.    Add mass to the cart and repeat the measurements.

 

 

Data Analysis

1.    Using the data in Table 9.1 plot force versus displacement graph. Draw the best-fit straight line through the data points and determine the slope of the line. The slope is equal to the effective spring constant, k. Record value in your data table.

2.    Calculate the spring potential energy and record in data table.

3.    Calculate the gravitational potential energy for each case and record in data table.

4.    Calculate the percent difference between the spring potential energy and the gravitational potential energy. Record in data table.

 

Note: Show #’s 2,3,& 4 on your calculations page.

Questions:

1.    Was energy conserved?

2.    Where did any “lost” energy go?

 

 

 

Only turn in; Title Page, Purpose, Data Tables, Graph, Calculations, and Questions