Circular motion activity - MYP PHYSICSmypphysics.weebly.com/.../circular_motion_activity.pdf ·...

CIRCULAR MOTION ACTIVITY Analyzing 𝐹𝑐 =𝑚𝑣2

𝑟

CIRCULAR MOTION ACTIVITY

From our notes last week, we know that objects that move in a circle require a force, and that force is called CENTRIPETAL.

The equation for this force is

𝐹𝑐 =𝑚𝑣2

𝑟where

𝐹𝑐 is the centripetal force (measured in Newtons)

𝑚 is the mass of the object (measured in kilograms)

𝑣 is the tangential speed (measured in meters/seconds)

𝑟 is the radial distance from the center (measured in meters)


From the equation, we can see that the centripetal force is affected by the mass, the tangential speed, and the radial distance.

The force is changed if we change the

* mass of the object being rotated

* how fast the object is moving

* and how far away the object is from the center of revolution.


The purpose/objective of this activity is to see how changing each variable in the equation affects the centripetal force.

Materials needed will include

1. Activity handouts

2. Meter Stick

3. Yarn

4. Various objects (Paper Clips, Binder Rings, Binder Clips, Large Eraser)

5. Stop watch (Cell Phones, Mobile Devices, or Chrome Books)

6. An open area to conduct the experiment. (Hallway or Classroom)


We will be doing this activity in groups of 4.

You may choose your own groups. (A lot of communication is needed. It’s easier to talk to people you know)

Make sure everyone in the group has a role.

A leader to keep the group on track.

A timer to record the time.

A recorder to record all the data.

A person to count the number of revolutions.

Due to the fact that this activity requires your group to work in various places,

I may not be able to monitor everyone at the same time. You are expected

to stay on task and behave properly especially in the hallway. Be courteous to

other classes. I will be moving back and forth to check on your progress. If you

have any question, send a member to find me.


There are 4 parts to the activity that has to do with data collection.

The time line to complete this is split between Monday and Tuesday.

All groups must complete the task by the end of the second day.

All groups will present their finding to the class on Wednesday/Thursday.

And wrapping up the work with a final summary of the activity with all the calculations and datasheets due by the end of class on Friday.


In order to calculate for the force, we first need to know how to calculate the tangential speed of an object undergoing uniform circular motion.

𝑣 =𝑑

𝑡

𝑣 =𝑑

𝑡

CIRCULAR MOTION ACTIVITY PART 1: CALCULATING TANGENTIAL SPEED

Objective: Calculating the tangential speed.

Materials Needed:


2. Meter Stick

3. Yarn




CIRCULAR MOTION ACTIVITY PART 1: CALCULATING TANGENTIAL SPEED

Procedure:

1. Gather the materials to conduct the experiment. Choose an object and measure its mass.

2. Find a safe area to conduct the experiment. Safe = far enough away from other groups so that no students impede the motion of the object.

3. Securely tie the object onto a string. Check to make sure the object will not fly off when it is spun.

4. Measure the length of the string about 35 cm and make a knot at that location.

5. Spin the object as fast as needed to keep the object moving in a circle and perpendicular to your hand.

6. Start the stopwatch when the object is moving correctly.

7. Stop the stopwatch after 10 complete turn.

8. Record the time for the 10-complete circles.

9. Divide the total time by 10 to get the period, T, the time it took the object to complete one revolution.

10. Repeat the experiment 4 times, record the data, and take the average value.

11. Use the equation 𝑣 =𝑑

𝑡=

2𝜋𝑟

𝑇to solve for the tangential speed.

correct

Incorrect

CIRCULAR MOTION ACTIVITY PART 2: CHANGING MASS CHANGES THE FORCE

The centripetal force equation, 𝐹𝑐 =𝑚𝑣2

𝑟, and we can see that the centripetal force is directly

proportional to the mass.

This means that if we increased the mass, we increase the amount of force.

The force increases only if we keep the tangential speed and the radial distance constant.


Objective: Show that increasing the mass of the object undergoing uniform circular motion would increase the centripetal force with the other variables were kept constant.

Materials Needed:


2. Meter Stick

3. Yarn





Procedure:


2. Find a safe area to conduct the experiment. Safe = far enough away from other groups so that no students impede the motion of the object.










𝑡=

2𝜋𝑟


12. Use the equation 𝐹𝑐 =𝑚𝑣2

𝑟to solve for the centripetal force.

13. Choose a different more massive object or add more mass to the object you were using.

14. Repeat steps 1 – 12 for the new mass.

15. Do your best to keep the tangential speed the same for the second mass by spinning at the same rate.

CIRCULAR MOTION ACTIVITY PART 3: CHANGING TANGENTIAL SPEED CHANG ES THE FORCE


𝑟, and we can see that the centripetal force is directly

proportional to the square of the tangential speed.

This means that if we increased the tangential speed, we increase the amount of force by a large factor.

The force increases only if we keep the mass and the radial distance constant.


Objective: Show that increasing the tangential speed of the object undergoing uniform circular motion would increase the centripetal force with the other variables were kept constant.

Materials Needed:


2. Meter Stick

3. Yarn





Procedure:


2. Find a safe area to conduct the experiment. Safe = far enough away from other groups so that no students impede the motion of

the object.










𝑡=

2𝜋𝑟




13. Repeat steps 1 – 12 for the same mass.

14. But this time increase the tangential speed by spinning faster.

CIRCULAR MOTION ACTIVITY PART 4: CHANGING RADIAL DISTANCE CHANGE S THE FORCE


𝑟, and we can see that the centripetal force is inversely

proportional to the radial distance.

This means that if we increased the radial distance, we decrease the amount of force.

The force decreases only if we keep the mass and the tangential speed constant.


Objective: Show that increasing the tangential speed of the object undergoing uniform circular motion would increase the centripetal force with the other variables were kept constant.

Materials Needed:


2. Meter Stick

3. Yarn





Procedure:


2. Find a safe area to conduct the experiment. Safe = far enough away from other groups so that no students impede the motion of

the object.










𝑡=

2𝜋𝑟




13. Repeat steps 1 – 12 for the same mass.

14. But this time increase the radial distance to 50 cm.

CIRCULAR MOTION ACTIVITY PART 5: PRESENTING DATA TO CLASS

Once each group have the opportunity to complete their data collection, the group will present their findings to the class. (Peer Review)

Students will compare results with other groups to determine the validity of their work.

CIRCULAR MOTION ACTIVITY PART 6: FINAL SUMMARY

Each group will write a summary of the activity with all the calculations and explanations of the relationship between the variables of the centripetal force equation.

The summary should include the following:

The process for calculating the tangential speed.

The results from each of the part of the experiment.

The feeling (tension) on the yarn as the variables changed.

The explanation why values are different in part 2, 3, and 4.

The entire packet is due by the end of Friday February 22, 2019.

Circular motion activity - MYP PHYSICSmypphysics.weebly.com/.../circular_motion_activity.pdf ·...

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