Download Materials

Physics Lab: Mass/Acceleration Relationship w/ Fixed Force (30 points) (page 1 of 3)
Background: In this investigation you will apply a fixed force to objects of different mass.
A net force applied to any mass should produce acceleration in the direction of the net
force. The computer should simplify acceleration measurement. Plotting collected data
should help confirm the currently accepted relationship (equation) between force, mass
and acceleration.
Materials:
PC
LabPro
Logger Pro
smart pulley w/ table clamp
4-500g masses
5 gram mass hanger
several 1-2 gram masses
balance to nearest gram
string
Graphical Analysis
Procedure:
1. Assemble the equipment as shown above. Place bricks so the cart will not slam into
the pulley. Put 2Kg of masses on the cart. To over come friction add mass to the
hanger so the cart just begins to roll. Record your system mass to the nearest gram.
Your system is everything that under goes acceleration. (cart/weights/hanger)
2. Plug the Photogate with a smart pulley into the DIG/SONIC1 port of the LabPro
interface. Connect the computer to the LabPro using the interface cable.
3. Boot LoggerPro. This program will automatically recognize a modern photogate.
(An old photogate must be manually configured.. Tap the green LabPro icon in the
upper left corner. Tap DIG/SONIC1 and select Photogate.)
Tap the new Photogate icon and select motion timing. Also tap the new Photogate
icon and select Select Distance or Length. Tap the carrot and select the type of pulley
you are using. It will probably be a 3 or 10 spoke pulley with string riding in a grove.
Close this window.
4. Set up data collection duration.
From the main screen select experiment/data collection and set mode to digital events
and end data collection after 20 events. (End data collection after 6 events for a three
spooked pullet.) Return to the main menu. Right click and delete the distance v/s time
graph. Also delete the acceleration v/s time graph. They are not needed for this study.
5. Note that your masses must fall far enough to turn the pulley twice or the interface will
not end data collection. Practice accelerating the cart a few times to ensure proper
alignment.
Physics Lab: Mass/Acceleration Relationship w/ Fixed Force (30 points) (page 2 of 3)
6. To measure the acceleration of this system, pull the cart back. Steady the masses so
they are not swinging. Activate the system to start data collection. After the interface
beeps, release the cart. Try to catch the cart before it hits the bricks.
7. You might need to adjust the axes to get a good look at the data. The slope of the
velocity v/s time graph represents the acceleration of the masses. To fit a straight line
to your data, drag-click and shade the area of interest. Do a linear fit. (Tap R=.)
Record this acceleration in the data table.
8. Repeat procedure 6 and 7 above, two more times. Good data should all be close to
each other. Redo any bad readings. Calculate and record the average.
9. Continue to repeat procedure 6 to 8 above, but each time remove 500g from the cart
until you measure the acceleration of the empty cart.
Calculations:
1. To determine the relationship between acceleration and mass, make a graph of
acceleration vs. mass and a graph of acceleration vs. reciprocal mass (1/Kg).
Draw a best fit straight line through each graph. If you are using a graphics program:
drag click the data of interest and select “R=” for the best linear fit. The data that
produces the best straight line is the preferred relationship. The graph that produces a
correlation coefficient closest to one, best describes the relationship. These graphs
should be submitted with your report.
Note: -- If the relationship between “a” and “m” is a directly proportional, a plot of “a”
vs. m should be near linear. The equation a/m=F is probably true. If “m” is
doubled, “a” should be doubled.
-- If the relationship between “a” and “m” is an inversely proportional, a plot of
“a” vs.1/m should be near linear. The equation F=ma is probably true. If “m” is
doubled, “a” is halved.
Name: ________________________ period: _______ (30 points)
(page 3 of 3)
Physics Lab: Mass/Acceleration Relationship w/ Fixed Force
Total
accelerating
mass (Kg)
Measured acceleration (m/sec2)
1/mass
(1/Kg)
Trial 1
Trial 2
Trial 3
Average
acceleration
(m/sec2)
(cart + 2Kg)
(cart + 1.5Kg)
(cart + 1Kg)
(cart + 0.5Kg)
( cart)
Questions: (2 point each)
1) For a fixed net force, if mass is doubled, what happens to the acceleration?
(Be specific.)
2) For a fixed net force, if the acceleration is halved, what can be said about the mass?
(Be specific.)
3) For a fixed net force, what is the fancy name for the relationship between acceleration
and mass?
4) Write an equation that describes the relationship between mass, acceleration and
force.
Summary: Your lab should contain the following:
6 points) Data Table
8 points) plot of acceleration vs mass w/ linear regression
8 points) plot of acceleration vs 1/mass w/ linear regression
8 points) answers to questions