CONSERVATION OF ENERGY LABORATORY ACTIVITY

ENERGY SKATE PARK

This lab uses a simulation that can be found at this link: https://phet.colorado.edu/sims/html/energy-skate-park/latest/energy-skate-park_all.html

Objectives

• Calculate gravitational potential energy
• Calculate kinetic energy
• Use conservation of energy to determine speed and/or height above a reference point
• Determine whether mass affects speed of an object under the influence of gravity
• Qualitatively reason about how friction affects the total gravitational potential energy and kinetic energy of a system

Procedure

1. Open the simulation. Play around with the controls to get a feel for how the simulation works. Make sure the boxes for "grid," "speed," and "stick to track" are checked. For now, turn friction off. Set gravity at 9.8 m/s^2 and the mass of the skater at 60 kg. Leave the skate track on a "U-shape."
2. Choose a height to release your skater from. Each tick on the grid represents 1 meter. Record your height below:

Initial height of skater: __________________________

1. Calculate the initial gravitational potential energy of the skater. Show your calculation below:

Initial gravitational potential energy of the skater: _______________________

1. Release the skater from the chosen initial height. Choose another point on the track above the ground to analyze using the energy sensor tool. Record the final height and final speed at this point:

Final height __________________

Final speed ___________________

1. Calculate the final gravitational potential energy, kinetic energy, and total energy at this point. Show your calculation below:

Gravitational potential energy______________________

Kinetic energy___________________________________

Total energy (sum of gravitational potential energy and kinetic energy) ___________________

1. Compare the total initial energy of the skater to the total final energy of the skater. Comment on your result.

1. Analyze the skater's energy at the bottom of the track. What kind of energy does the skater have at the bottom of the track?

1. Use the energy sensor tool to determine the skater's speed at the bottom of the ramp. Record the speed below:

Speed at bottom of the ramp:___________________

1. Calculate the kinetic energy at the bottom of the ramp. Show your calculation below:

Kinetic energy at the bottom of the ramp: _______________

1. How does the kinetic energy of the skater compare to the total initial energy of the skater? Comment on your results.

1. Change the mass of the skater and release the skater from your initially chosen height. How does changing the mass of the skater affect the speed of the skater at the bottom of the ramp? Explain your answer using physics principles.

1. Add some friction to the skate ramp. Release the skater from your initially chosen height and observe what happens. Use the energy sensor to comment on the total energy.
2. How does the gravitational potential energy change over time?
3. How does the kinetic energy change over time?
4. How does thermal energy change over time?
5. How does the total energy change over time?

Questions

1. A roller coaster of mass 1000 kg moves with a speed of 10 m/s at the top of a hill that is 20 m above the ground. How fast is the roller coaster moving when it reaches the bottom of the hill at ground level? (ignore frictional effects and air resistance)

1. A pendulum with a mass of 0.25 kg is released from a position in which the bob is 12 cm above the low point in its swing. What is the speed of the bob as it passes through a point 10 cm above the low point in its swing? (ignore frictional effects and air resistance)