In this lab you will look at an cart moving down an inclined plane and
determine it's efficiency. To do this you will have to calculate the total
amount of energy that the cart has at the top of the ramp (Gravitational
Potential Energy) and compare it to the amount of energy at the bottom
(Kinetic Energy)
To gather the data for this lab you will have to use
logger pro and photo gates connected to a Lab Pro. Photo gates are essentially a light beam
that when broken can record a time. To determine final velocity, you
will use this instrument to determine the time that a 2.5cm "picket fence" passes through the beam. This will allow you determine the cart's
final velocity.
Using one group member's computer, plug into a lab pro.
Often, the machine will have to load a driver to run this device, but this
should be done automatically. Once set up, click on
photogate.cmbl and
the a logger pro window will open up on your computer. You should now be set
to collect data.
Once set up, place your cart on the top
of the track. Measure the perpendicular distance from the black mark
on the cart of the cart to the desk. From this value subtract the height of
the finish line i.e. from below the photogate to the desk (remember the potential energy is
proportional to the total 'height' drop of the cart). This will allow
you to calculate the “total” potential energy of the system.
MAKE SURE THAT
WHEN THE CART IS NOT ON THE TRACK IT IS FLIPPED ON ITS SIDE SO IT DOES NOT
ROLL OFF THE DESK. ALSO, THESE CARTS HAVE MAGNETS IN THEM - DO NOT
BRING THEM NEAR YOUR LAPTOP.
From this height, first press the "collect button" on
logger pro and then release the cart. Use the time data from logger
pro to calculate the final velocity of the cart once it reaches the end of
the track. To do this you must take the length of the picket fence gap
breaching the photo gate (0.025m) and divide it by the time it took to pass through them (i.e.
v=d/t). Use this
to information calculate the “useful” kinetic energy. Be sure that this paper
strip do not, at any time, rub or strike the photo gate. Make sure that
you do not allow the cart to "CRASH" into the end of the cart. Catch it
before the end being sure that it does not cross the photo gate again.
Take two trials for your cart for four separate
heights and record this data in the table below.
Table 1: Cart Trial Data
Once complete, clean up all of your desk leaving it as
you found it at the start of the lab.
Taking the “average” efficiency of your two trials from
each height and place it in another table (Table 2: Average Efficiencies for
Cart Trials). From this data, plot an “Efficiency vs. Height” graph
using “Graphical Analysis”.
Using Graphical Analysis
You will be doing a significant amount
of graphing in Grade 11 physics this year. As such, it is important
that you familiarized yourself with "Graphical Analysis".
First open the program and enter in
your data into the table of the left side of the screen. As you do so,
a graph will begin to appear.
. Click this and add an appropriate trend
line.