Reading Quiz 9 Key

Reading Quiz 9 Key

Due 3:30 pm, Tuesday, September 29th

Physics 105, Fall Term, 2009


Reading: Chapter 5.2-5.3

Did you complete the reading assignment?

Yes
No

KEY CONCEPTS:

1) Kinetic Energy is the energy in the movement of objects.

2) Gravitational potential energy is the potential an object has to move produced by a gravitational force.

3) Elastic potential energy is the potential an object has to move produced by the force from a spring or other elastic system.

Energy is the amount of work that can be done by a force. We will investigate the different types of mechanical energy in this reading quiz.

Exercise 1

Go to: http://phet.colorado.edu/sims/energy-skate-park/energy-skate-park_en.jnlp

Click the 'Bar Graph' button on the right side of the applet. Adjust the track size and shape by pulling on the circles at the joints of the lines. You can also change the starting point of the skater by clicking and dragging him to a specific part on the track.

Where is the kinetic energy of the skater the greatest?

Highest point on the ramp
Lowest point on the ramp
Half way between high and low point on the ramp

Where is the kinetic energy of the skater the least?

Highest point on the ramp
Lowest point on the ramp
Half way between high and low point on the ramp

What is the determining factor for the kinetic energy of the skater?

Now press the 'Choose Skater' button at the top right of the applet. Change from the Phet Skater to the bug. How does this affect the kinetic energy? Why does it affect it in this way?

Change back to the Phet Skater. Where is the gravitational potential energy of the skater the greatest?

Highest point on the ramp
Lowest point on the ramp
Half way between high and low point on the ramp

Where is the gravitational potential energy of the skater the least?

Highest point on the ramp
Lowest point on the ramp
Half way between high and low point on the ramp

What is the determining factor for the gravitational potential energy of the skater?

Click the 'Potential Energy Reference' checkbox near the top right of the applet. Drag the reference line to the highest point that the skater reaches on the track. How has this changed your values of potential energy?

Why is potential energy affected by changing this reference point when kinetic energy is not changed by it?

Change the location to Jupiter on the right side of the applet. How does the maximum potential energy change?

Increases
Decreases
Stays the same

Explain the result from the question above.

Exercise 2

Now go to: http://phet.colorado.edu/sims/mass-spring-lab/mass-spring-lab_en.html

You can see the energy of any mass you put on any of the springs by clicking the bubble for that specific spring in the box labeled 'Show Energy of'. Place a 50g mass on spring 1, a 100g mass on spring 2, and a 250g mass on spring 3. Wait until they stop moving.

Look at the energy bar graphs for each spring, which has the most elastic potential energy?

Spring with 50g mass
Spring with 100g mass
Spring with 250g mass
They are all the same

Now view the energy graphs of each spring when each spring is stretched to the same distance. What determines the the elastic potential energy for these springs?

Mass held by spring
Length of the spring
Distance spring is stretched
Height spring is off the ground

Replace the 250g spring with the other 100g spring. Now view the energy graph of spring 3 and change its softness to the maximum amount and then the minimum amount by using the scroll bar near the top right of the applet. What changes about spring 3 when the spring softness is changed? (select all that apply)

Mass held by spring
Elastic potential energy of the spring
Distance spring is stretched
Height spring is off the ground

What variable has the greatest affect on the elastic potential energy of the spring?

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Was there anything that you didn't understand in the reading assignment?  What was confusing to you?


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