141 Lab Final Flashcards
Do significant figures count zeros before the number?
no
How many sig figs can you record on an instrument like a ruler?
as many numbers can be read on the ruler PLUS ONE estimated number
When are trailing zeros significant?
only if the decimal point is shown
How many significant figures in 0.00334?
3
How many significant figures in 1.3800 × 10^4?
5
How many significant figures in 34.00?
4
When multiplying or dividing numbers, what should be the number of sig figs?
the number of significant figures equals the smallest number of significant figures in any of the original numbers
8.3 m × 1045 N equals what?
8700 Nm (not 8673.5 Nm)
What do axis labels on Excel graphs need to include?
the units in parentheses
What should be displayed on graph?
equation and R2
What does every reported value need?
an uncertainity measurement
How many digits should uncertainity be rounded to?
uncertainity should be rounded to 1 sig fig
How should uncertainty and the measurement be the same?
uncertainty and the measurement should be rounded to the same decimal place
How do we eliminate the systematic error from the camera’s shutter in tracker?
turn the video horizontally
When using the hop frog method to calculate velocity where should you not have a value?
the first and last cells in the column
In projectile motion, what is true of velocity and acceleration in the x-direction?
Acceleration is 0, so velocity should be constant in the x-direction
How can you eliminate the systematic error from the camera’s shutter in projectile motion?
use a matched data set
use equal number of data points on the uptrip and downtrip whenever graphing
What should you do to times from tracker?
re-zero the times so that zero is included on the x-axis of a “versus time” graph
When the glider is moving to the left what do you want to do to the axis in tracker? (like in the gliding mass)
You want to call the leftwards direction positive to get positive values
Have to click-and-drag the vertical tick-mark on the axis 180º
Then, move axis to the lower right-hand corner
What do you always need to do in tracker?
1) Set your reference measurement
2) Set your axis so that you get positive values
In lab 4 (with the gliders), explain what the slope of Fnet versus M2 equals?
The slope of Fnet versus M2 equals gravity (g)
Since our force equation is Fnet=gM2, if we treat this like y=mx+b our slope is gravity
How did we find Fnet as a function of M2 in lab 4 (with the gliders)?
We calculated individual accelerations for varying amounts of added weight
Then we used the acceleration*total mass to generate Fnet
Then, we have Fnet as a function of M2
How to find kinetic energy of the pendulum?
first, need to find the speed (v) which is going to be a combination of x and y components
find the distance between the two successive points using “s=” formula and then divide by the time between two points (we used 0.0333 seconds in lab)
When calculating the distance between two points (like with the pendulum) which cells will not be filled?
the first cell will NOT be filled, but the last cell will be filled
What is the first step we do to measure potential energy in the pendulum?
set the height at the bottom of the swing to equal 0
this allows us to have potential energy=0 at the bottom of the swing
do this by finding the y-coordinate at the lowest point of your tracker measurements
What do we do in excel to measure potential energy of the pendulum?
use the “h=” formula and create a new column adjusted for height
then multiply this column by mg
*this column will be empty at the first cell
What does the y-intercept of a v^2 versus h graph tell us? (pendulum)
the velocity at the bottom of the swing
can multiply by 1/2*m to get the kinetic energy
since h=0, we know we have all kinetic energy and no potential energy
therefore, the kinetic energy at the y-intercept equals the total energy of the system
What does the x-intercept of a v^2 versus h graph tell us? (pendulum)
the release height/the maximum height
there is no velocity, so we know that we are at the maximum height/all energy is equal to potential energy
What was the point of the circular motion lab?
to prove that although the puck’s speed doesn’t change, it is accelerating because it’s direction changes
Centripetal (radial) acceleration
points towards the center of the circle
due to velocity changing directions not magnitude
caused by familiar forces
always have centripetal acceleration when moving in a circle
Difference between angular and centripetal acceleration
angular acceleration is an angular quantity whereas centripetal acceleration is a linear quantity (m/s2)
angular acceleration just refers to if angular velocity is slowing down or speeding up
can be rotating without an angular acceleration (magnitude not changing)
What do you need to find for centripetal acceleration?
it is a vector quantity, so need to know magnitude and direction
What is the first step of finding centripetal acceleration using the paper circle?
measure the distance between a couple of points and divide by 0.00333 seconds (the amount of time between each)
average these velocities together to get a single constant velocity
Translating final and initial velocities on paper circle?
the final and initial velocities should be the same length
translate the final velocity to the initial velocity TAIL to TAIL
measure the change in velocity between final and initial (vf= vi + ∆v)
∆v should be tip to tail with vi (∆v has tail at the head of vi)
What is the final step in finding the centripetal/radial acceleration using the paper circle?
divide the found ∆v by the ∆t between vf and vi
What is an alternate way to find centripetal/radial acceleration using the paper circle?
use the formula a=v^2/R
square the first found, constant velocity and divide by the radius of the circle
Why do you get more torque further from the hinge?
bigger distance the torque can act through
Archimedes principle
bouyant force is equal to the weight of the displaced force
What happens if an object’s weight is greater than the weight of the fluid displaced?
the object will sink
the object’s weight is greater than the bouyant force
What happens if an object’s weight is less than the weight of the fluid displaced?
the object will float
the bouyant force is greater than the weight and the object floats
What force does a scale most directly read?
the normal force
or tension if the scale is hanging
How do you find the volume of an object submerged underwater?
use a force diagram and equations for the bouyant force (these are written down)
How do you find the density of an object submerged underwater?
first, find the mass from the scale reading of weight outside water (divide by gravity)
then, use a force diagram to solve for the volume using buoyant force
Simple harmonic motion
Results when an object is subject to forces which give it an acceleration proportional to its displacement from its equilibrium position
Graph of applied force (newtons) versus elongation (meters)
Slope tells us the spring constant in N/m
How do you change the applied force on a spring to graph applied force as a function of elongation?
Change the weight hanging from the spring
This will change the applied force (gravity)
Does period depend on amplitude? How do we experimentally prove this?
No! Can prove this by changing the release amplitude and measuring the period
The period will not change
Does period depend on applied force/added mass?
yes
Graph of period (in s^2) versus mass (kg)
another way to calculate a spring constant through slope
need to rearrange a formula to calculate (formula is written down)
generate this graph by measuring the period of different applied forces/ added mass
How to find a spring’s effective vibrating mass?
should be the “negative” mass on the x-intercept of a s^2 versus kg graph
How many sig figs based on a graph?
if using the slope and/or the y-intercept use 3 sig figs based off of a graph
What do excel trig functions automatically calculate in?
radians
need to use formula if importing degrees
What should be the same in lab one?
the average of the calculated velocities and the slope of position versus time graph
since velocity is constant in lab 1
How many points do you count from between the two vectors on the circle to determine ∆t?
??? Figure out
