Archimedes’ Principle r1.04

The Snapshot button is used to capture the screen. The Journal is where snapshots are stored and viewed. The Share button is used to export or print your journal to turn in your work. Introduction Journals and Snapshots Note: You may want to take a snapshot of the first page of this lab as a cover page for your journal. Each page of this lab that contains the symbol should be inserted into your journal. After completing a lab page with the snapshot symbol, tap (in the upper right corner) to insert the page into your journal. Archimedes’ Principle

Lab Challenge What force causes some things to float while others sink? Archimedes’ Principle

Background Archimedes (287 to 211 B.C.) lived in the Greek colony of Syracuse on the island of Sicily, and is considered to be one of the greatest mathematicians of all time. Although there are many images of Archimedes, no true likeness has survived. One of his discoveries, that has lived on, is that an object submerged in a fluid displaces a volume of the fluid that is equal to the volume of the object. Archimedes’ Principle

...Background Following in Archimedes footsteps, we will observe what happens to objects that are submerged and try to determine the difference between objects that float and those that sink. Archimedes’ Principle

Collect all of these materials before beginning the lab. Force Sensor Overflow Can 2 Small Cups String Rod Stand Right Angle Clamp Short Rod Object to submerge Water Ruler Balance (1 per class) Materials and Equipment Note: Graduated cylinder not used in this lab. Archimedes’ Principle

C. Show that the change in net force on the object before and after submersion is equal to the weight of displaced water. D. Measure the net force(s) acting on an object. Hint: This step is used twice A. Calculate the force due to gravity on the volume of displaced water (weight in N). B. Completely submerge an object in water, collecting the volume of water displaced by the object. Sequencing Challenge The steps to the left are part of the procedure for this lab activity. They are not in the right order. Determine the correct sequence of the steps, then take a snapshot of this page. Archimedes’ Principle

Setup 1.Attach the Force Sensor to the rod stand using a short rod and the right angle clamp. 2.Connect the Force Sensor to your SPARK Science Learning System. 3.Press the zero button on the Force Sensor. 4.Place the overflow can below the force sensor. 5.Tie a loop of string to the object, long enough to allow the object to be submerged completely in the overflow can when hung and lowered from the force sensor. Archimedes’ Principle

Setup 6.Place a dry cup (catch basin) under the spout of the overflow can. 7.Fill the Overflow Can with water to the limit. Note: To reach the fill limit of the can, overfill the can allowing the excess water to pour from the spout. When the spout has stopped dripping, the can will be completely filled. Be sure to empty the catch basin after doing this. Archimedes’ Principle

Setup Q1: Why is it important to fill the water to the point that begins to run out of the spout of the Overflow Can? a)to ensure we capture all the water that is displaced by the mass b)to make sure we maximize the dilution c)to insure that we minimize the amount of water that is captured d)to eliminate the need to refill the can Make your selection below then take a snapshot of this page. Archimedes’ Principle

Collect Data 1.Use a balance to measure the mass of the empty cup (catch basin) in kg. 2.Record the cup's mass in the table to the left. *To Enter Data into a Table: 1.Tap to open the tool palette. 2.Tap then tap a cell in the data table to highlight it in yellow. 3.Tap to open the Keyboard screen. Archimedes’ Principle

*To Enter Data into a Table: 1.Tap to open the tool palette. 2.Tap then tap a cell in the data table to highlight it in yellow. 3.Tap to open the Keyboard screen. Collect Data 3.Measure the mass of the object you will submerge in the water, in kg. 4.Record the object's mass in the table to the left. Archimedes’ Principle

*To Enter Data into a Table: 1.Tap to open the tool palette. 2.Tap then tap a cell in the data table to highlight it in yellow. 3.Tap to open the Keyboard screen. Collect Data 5.Measure the dimensions of the object then calculate its volume. 6.Record the object's volume in the table to the left. Archimedes’ Principle

Make your selection below then take a snapshot of this page. Collect Data Q2: Why is it important to measure the mass of the empty cup? a)to be sure the cup is not too heavy for the experiment b)to make sure the cups are of equal mass c)to calculate the cup's body mass index d)to ensure we can get an accurate measure of the amount of water displaced by the hanging mass Archimedes’ Principle

7.Use the string loop to hang the object from the force sensor hook. Make certain that the object is not swinging before recoding data. 8.With the object not yet submerged, tap to begin recording data. 9.Tap to record the initial net force acting on the object. Collect Data Archimedes’ Principle

Collect Data 10.Loosen the thumbscrew mounted to the crossbar and rod stand and slowly lower the object into the overflow can. Displaced water from the overflow can should pour into the empty cup (catch basin). 11.Tighten the thumbscrew holding the object fully submerged, but not touching the bottom of the can. Note: If water fails to pour from the spout when the object is submerged you may need to clear the spout on the overflow can. Water will sometimes form a seal across the spout opening with enough surface tension to prevent any overflow. To clear it, first remove the object from the water, then blow softly down the spout of the overflow can clearing the passage. Archimedes’ Principle

12.With the object fully submerged, tap a second time to record the new net force acting on the object. 13.Tap to stop data collection. Collect Data Archimedes’ Principle

*To Enter Data into a Table: 1.Tap to open the tool palette. 2.Tap then tap a cell in the data table to highlight it in yellow. 3.Tap to open the Keyboard screen. Collect Data 14.Use a balance to Measure the mass of the cup (catch basin) and water that has overflowed from the can. 15.Record that mass in the table to the left. Archimedes’ Principle

Analysis If the mass of the object does not change when it is submerged, but the net force does, we must be observing the action of a second force on the object. This force is called the Buoyant Force. The force on the submerged object is the resultant of the vector addition of the force of gravity and the buoyant force acting on the object. MgResultant Buoyant Force Archimedes’ Principle

Analysis The two tables on the next page (page 21) will be used to answer the Analysis questions on pages 22 and 23. Please refer back to these tables for any of the measured quantities in this lab. Archimedes’ Principle

Analysis 1.Calculate the mass of the displaced water in kg by subtracting the mass of the empty cup from the mass of the displaced water and cup together. 2.In the text box below, calculate the weight of the displaced water in newtons by multiplying the mass of the water by the acceleration of gravity (9.81 m/s 2 ). 3.In the text box below, calculate the buoyant force by subtracting the force submerged from the force due to gravity. Archimedes’ Principle

Analysis 4.In the text box below, compare the mass of the object to the mass of the displaced water. 5.In the text box below, compare the volume of the object to the mass of the water displaced. 6.In the text box below, compare the buoyant force to the weight of the water displaced, then take a snapshot of this page. Archimedes’ Principle

Synthesis 1.What would a submerged object do if the buoyancy force were greater than the force of gravity on the object? Archimedes’ Principle

Synthesis 2. Imagine a person in a deep pool. What happens to the person if they: a)let the air out of their lungs? Why? b)take a deep breath and hold it? Why? Archimedes’ Principle

Make your selection below then take a snapshot of this page. Multiple Choice Question 1.A completely submerged object displaces its own _________________. a)density of fluid b)weight of object c)volume d)mass Archimedes’ Principle

Make your selection below then take a snapshot of this page. Multiple Choice Question 2.What is the buoyant force acting on a 20-ton ship floating in the ocean? a)20 tons b)less than 20 tons c)more than 20 tons d)depends on the density of seawater Archimedes’ Principle

Make your selection below then take a snapshot of this page. Multiple Choice Question 3.A lobster crawls onto a bathroom scale submerged at the bottom of the ocean. Compared to its weight above the surface, the lobster will have an apparent weight under water that is ________________. a)less b)the same c)more d)depends on the density of seawater Archimedes’ Principle

You have completed the lab. Congratulations! Please remember to follow your teacher's instructions for cleaning-up and submitting your lab. Archimedes’ Principle

ALL IMAGES WERE TAKEN FROM PASCO DOCUMENTATION, PUBLIC DOMAIN CLIP ART, OR WIKIMEDIA FOUNDATION COMMONS: References Archimedes’ Principle