https://phet.colorado.edu/sims/html/hookes-law/latest/hookes-law_en.html

http://www.thephysicsaviary.com/Physics/Programs/Labs/EnergyTransformationLab/index.html

Unit 2 Lab 2 Elastic Potential Energy and Conservation of Energy

Part 1 Hooke’s Law

Open Hooke’s Law Simulation (link on Canvas).

https://phet.colorado.edu/sims/html/hookes-law/latest/hookes-law_en.html

After the simulation opens, click on the “Energy” option (on right).

Select the Force Plot option and set the Spring Constant setting to 100 N/m.

Hooke’s law was discovered by Robert Hooke, a contemporary of Newton. It says that springs exert forces proportional to the distance they are stretched or compressed away from their natural length.

In equation form: , where F is the force the spring exerts, k is called the Spring Constant and is a property of the spring itself, and d is the distance the spring is extended or compressed.

Sometimes it is written as , because the direction of the force is opposite the direction the string is stretched or compressed. We will leave the negative sign out and focus on the magnitude of the force, without regard to direction.

The Spring Constant, k, has to be measured. Use the simulation to understand how to measure the Spring Constant. If we solve Hooke’s Law for the spring constant, it is , with the unit of force per distance. Standard unit would be .

Set the spring constant to the value in the table below, stretch or compress the spring to any distance you choose, record the displacement and force, and calculate the Spring Constant, which should come out close to the setting value. Then change the spring constant to the next value and repeat.

To stretch or compress a spring, work must be done. In the simulation (with the “Energy” box checked under the Force Plot option) the blue area under the Force vs. Displacement graph represents the work done. It is a triangle with a base of the displacement value and a height of the force value.

If we substitute Hooke’s Law formula for the force, we get the elastic potential energy stored in the spring.

Use this formula to add the elastic potential energy value to the table above for the displacement and spring constant for each row.

Part 2: Elastic Potential Energy in a Spring

Click on the link in the Lab Canvas to open Energy Transformations Lab.

(http://www.thephysicsaviary.com/Physics/Programs/Labs/EnergyTransformationLab/index.html)

Click “Begin”.

Set the mass using the blue arrows on the lower left of the simulation. Each student should set the simulation mass and spring constant to a unique value, different from other students. For best results, choose a relatively high mass (greater than 100 kg) and a relatively low spring constant (below 1000 N/m). Your instructor may assign values for each student.

Record your mass and spring constant in the table below.

Click “Set Trevor” and click on “Pull Back” 10 times. This should set the spring to a compression of 2.0 meters.

Click “Fire Trevor” and when you see the ice rink graphic, hover the mouse over the “Start Timer” button and click it when Trevor passes over the blue line to start the timer and again when he passes over the 2nd blue line to stop the timer. The accuracy of your timing will affect your grade, so you might want to do several trials until you get a consistent result.

Record your data below and do the calculations indicated.

If you did everything correctly, your kinetic energy ought to be about the same as the elastic potential energy in the spring.

2

Unit 2 Lab 2 Elastic Potential Energy and Conservation of Energy

Part 1 Hooke’s Law

Open Hooke’s Law Simulation (link on Canvas).

https://phet.colorado.edu/sims/html/hookes-law/latest/hookes-law_en.html

After the simulation opens, click on the “Energy” option (on right).

Select the Force Plot option and set the Spring Constant setting to 100 N/m.

Hooke’s law was discovered by Robert Hooke, a contemporary of Newton. It says that springs exert forces proportional to the distance they are stretched or compressed away from their natural length.

In equation form: , where F is the force the spring exerts, k is called the Spring Constant and is a property of the spring itself, and d is the distance the spring is extended or compressed.

Sometimes it is written as , because the direction of the force is opposite the direction the string is stretched or compressed. We will leave the negative sign out and focus on the magnitude of the force, without regard to direction.

The Spring Constant, k, has to be measured. Use the simulation to understand how to measure the Spring Constant. If we solve Hooke’s Law for the spring constant, it is , with the unit of force per distance. Standard unit would be .

Set the spring constant to the value in the table below, stretch or compress the spring to any distance you choose, record the displacement and force, and calculate the Spring Constant, which should come out close to the setting value. Then change the spring constant to the next value and repeat.

To stretch or compress a spring, work must be done. In the simulation (with the “Energy” box checked under the Force Plot option) the blue area under the Force vs. Displacement graph represents the work done. It is a triangle with a base of the displacement value and a height of the force value.

If we substitute Hooke’s Law formula for the force, we get the elastic potential energy stored in the spring.

Use this formula to add the elastic potential energy value to the table above for the displacement and spring constant for each row.

Part 2: Elastic Potential Energy in a Spring

Click on the link in the Lab Canvas to open Energy Transformations Lab.

(http://www.thephysicsaviary.com/Physics/Programs/Labs/EnergyTransformationLab/index.html)

Click “Begin”.

Set the mass using the blue arrows on the lower left of the simulation. Each student should set the simulation mass and spring constant to a unique value, different from other students. For best results, choose a relatively high mass (greater than 100 kg) and a relatively low spring constant (below 1000 N/m). Your instructor may assign values for each student.

Record your mass and spring constant in the table below.

Click “Set Trevor” and click on “Pull Back” 10 times. This should set the spring to a compression of 2.0 meters.

Click “Fire Trevor” and when you see the ice rink graphic, hover the mouse over the “Start Timer” button and click it when Trevor passes over the blue line to start the timer and again when he passes over the 2nd blue line to stop the timer. The accuracy of your timing will affect your grade, so you might want to do several trials until you get a consistent result.

Record your data below and do the calculations indicated.

If you did everything correctly, your kinetic energy ought to be about the same as the elastic potential energy in the spring.

2