PhET Simulation (colorado.edu)

QUESTION 1.1

Q1

Set the force equal to 1 N.

Click Go and let this run for at least 14 seconds.

What eventually happens to the ladybug?

It moves to the center of the disk

It is thrown off the disk

It catches fire

Nothing ever happens to it

QUESTION 1.2

Q2

What is thetorque on the disk by the applied force, assuming the disk is in the x-y plane?

(hint: What axis is it spinning around?)

1 Nm in the x direction

4 Nm in the x direction

4 Nm in the y direction

4 Nm in the z direction

QUESTION 1.3

Q3

Thenet torque will create what?

(Hint: What axis is it spinning around, and will it cause clockwise or counter-clockwise rotation?)

Angular acceleration in the z direction

Angular acceleration in the -z direction

Angular acceleration in the x direction

Angular acceleration in the -x direction

QUESTION 1.4

Q4

As the angular velocity increases, what happens to the centripetalforce on the lady bug?

It goes up

it goes down

it is unaffected

QUESTION 1.5

Q5

What force must be responsible for thecentripetal force that keeps the lady bug moving in a circle?

Static friction

Gravity

Torque

Moment of Inertia

QUESTION 1.6

Q6

Click "reset all" and make sure the applied force is set to 1N. Hit go while closely watching the acceleration vector is the diagram.

Does the acceleration ever point directly to the center of the disk? Are you sure?

(after solving the next 4 questions you might want to revisit this one and change your answer)

It starts pointing to the direct center and stays there

after a short period of time it points to the direct center

Over time the acceleration vector points closer and closer to the center, but never perfectly pointing at it so that angular velocity keeps increasing

QUESTION 1.7

Q7

Click "reset all" again and make sure the applied force is set to 1N.

Hit go, wait about 2 seconds, and set the force of brake to 1 N. Hit enter and observe.

Which best describes the motion of the wheel.

The angular velocity of the wheel grows even after the break is applied.

The angular velocity of the wheel grows, and then becomes constant after the break is applied.

The angular velocity of the wheel grows then lowers to zero after the break is applied.

QUESTION 1.8

Q8

When running the experiment inQ7 question, what happened to the acceleration vector?

it continually grew larger

It grew larger than shrank

It grew larger until the brake was applied, and then it stayed a constant length pointing toward the center.

QUESTION 1.9

Q9

Click "Reset all" and set the appliedF=force back to 1 N. Hit go.

After a few seconds, set the brake force equal to 3N and hit enter.

Which best describes the motion of the disk?

The angular velocity of the wheel grows even after the break is applied.

The angular velocity of the wheel grows, and then becomes constant after the break is applied.

The angular velocity of the wheel grows then lowers to zero after the break is applied.

QUESTION 1.10

Q10

When running the experiment in Q9, what happened to the acceleration vector?

it continually grew larger

It grew larger than shrank never pointing toward the direct center

It grew larger until the brake was applied, and then it stayed a constant length pointing toward the center.

QUESTION 1.11

Q11

What is the net torque right after the break force is applied in Q9?

2 in the -x direction

2 in the z direction

8 in the z direction

8 in the -z direction

QUESTION 1.12

Q12

1. Click the Moment of Inertia Tab at the top.
2. To best see the graphs, set the vertical scale of the torque graph to show a range of 20 to -20.
3. Set the vertical scale of theMoment of Inertia graph to show a range of 2 kg m2to - 2 kg m2
4. Set the vertical scale of theangular acceleration graph to show 1,000 degrees / s2to -1000 degrees / s2
5. Calculate the moment of Inertia for the disk with the given information. and check it versus the value given in the graph on the simulation.
6. Add a checkmark next to ruler on the left side of the screen.
7. Using the ruler to measure, click andhold the curser over the disk so that the curser is 2 m away from the center of the disk.(this will beinthe green zone)
8. While continuing to hold left click, move your mouse to apply a force.
9. Look at the graph and try to apply a force that creates a torque of 10.

Calculate what the applied force must have been. What is that applied force?

10N in the y direction

10N in the z direction

5N in the y direction

5N in the z direction

QUESTION 1.13

Q13

Imagine that you created a disk with thesame radius and massas the current disk, but it had a hole in its center(donut shaped).Predict how the moment of inertia of this new disk would compare to the original disk.

The Moment of Inertia would go down

The Moment of Inertia would stay the same

The Moment of Inertia would go up

QUESTION 1.14

Q14

In the simulation, set the inner radius equal to 2. Set the disk in motion and check your prediction by looking at the moment of inertia graph. What really happened to the moment of inertia of the new disk?If this does not match up withyour prediction in Q13 think aboutwhere you think you messed up in your reasoning.

The moment of inertia went down

The moment of inertia stayed the same

The moment of inertia went up

QUESTION 1.15

Q15

Fill in the blanks: When the mass of an object increases, the moment of inertia ________________. When the distance of the mass from the axis of rotation increases, the moment of inertia ___________________.

Increases, Increases

Increases, decreases

Decreases, Increases

Decreases, decreases