Name ______Per. _____

Pendulum Lab – Work & Conserving Energy

The pendulum was one of the first devices used to study time, the force of gravity, and other aspects of physical science. Energy of motion carries the swinging pendulum to its highest point at the end of the swing. Except on the highest and lowest points, both potential and kinetic energies are present in constantly changing proportions.

  1. Is the pendulum doing work? ____ How do you know? ______
  2. Work, Potential Energy, and Kinetic Energy all have the same unit; what is it? ______
  3. Which position(s) on the pendulum below has the most potential energy? 1, 2, 3, 4, or 5
  4. Which position(s) on the pendulum below has the most kinetic energy? 1, 2, 3, 4, or 5
  5. How does a pendulum demonstrate the law of conservation of energy?

Problem: What aspect of a pendulum will affect its period (time for one complete swing back and forth) the most: height released, weight, or length?

Prediction: ______

Testing Distance from Rest Position (Height released):

  1. Hang a 100 g mass from a 1 meter length of string and let it go from different distances. You decide what three distances. For each distance, count the number of complete swings (back AND forth) per minute. Also, determine how many seconds it takes for the pendulum to complete on swing. Record your data below.

Trial / Distance from Resting Point / # of complete swings per minute / Period (seconds per complete swing)
1 (100g)
2 (100g)
3 (100g)

Did distance make a big difference in the period? ______At which height did the pendulum do the most work? ______

Testing Weight:

  1. Repeat the process with the exact same length of string and distances from before, but this time, use the 200 g mass. Record your data below:

Trial / Distance from Resting Point / # of complete swings per minute / Period (seconds per complete swing)
1 (200g)
2 (200g)
3 (200g)

Did more mass make a big difference in the period? ______During which of these three trials did the pendulum do the most work? ______

Testing Length:

  1. For this test, always use a 200 g mass and your swing 10 cm away. You will only be changing the length of the string:

Length / # of complete swings in a minute / Period
(seconds per swing)
25 cm
50 cm
75 cm
100 cm
125 cm

Did changing the length of the string make a big difference in the period? ______During which trial of this entire lab did the pendulum complete the most work? ______

Analysis

  1. What determines the period of a pendulum? Height of swing, Mass of weight, or Length of string?
  1. What two variables determine the amount of work the pendulum does? Height of swing, Mass of weight, or Length of string?
  1. What two variables determine the amount of potential energy a pendulum has? Height of swing, Mass of weight, or Length of string?
  1. What would be the period of a pendulum 100 cm long, with a 500 g mass, released at a distance of 50 cm from its rest position?
  1. What are at least three sources of error or limitation to collecting data in this lab?
  1. Differentiate between kinetic energy and potential energy.
  1. What are the two different types of potential energy?
  1. Identify the type of energy stored in a stretched bungee cord.
  1. Explain how sunlight is converted into potential energy by plants.
  1. What does “mechanical energy” mean?
  1. Define the term “efficiency” as it relates to energy.
  1. Describe two ways mechanical energy can be transformed into nonmechanical energy.
  1. .
  1. .
  1. If you do 425 J of work to push a 75 N box up a ramp until the box is 2.5 m above the ground, what is the efficiency of your work? Hint: you need to use both equations.

Work = F X d Eff = Work Out X 100 = ______%

Work In

  1. Why will your pendulum eventually slow down and stop?
  1. How does that (#14) STILL showing the law of conservation of energy?