Physics Lab final
Check how well the conservation principle of mechanical energy holds.
Find the percent difference between the initial and final mechanical energy Difference/average
How well is the total angular momentum conserved during the collision.
Find the percent difference.
If there is acceleration what should the position vs. time graph look like?
Position vs. time data should lie along a curve
Static Friction
Static Friction=F(normal)µ -Dependent of the two objects in contanct
If you drop a feather and penny in air, which one would hit the ground first?
The penny will hit first
How is gravity related to slope?
g=(2π/slope)² slope=2π/√g
The coefficient of static friction is always _______ the coefficient of kinetic friction.
greater than
If the force applied on an object is greater than the force of kinetic friction the object will travel with ________ velocity.
increasing
What are the units for the period of a pendulum from the equation above?
seconds
Considering our pulley system with a mass falling at a constant acceleration, what should the general shape of its velocity vs. time graph look like.
straight line
Given the equation above, the slope of the graph of acceleration vs. the mass ratio is (see equation in quiz 6)
the acceleration due to gravity
What is the purpose of the friction rider?
to counter balance the kinetic friction in the system
The period is independent of:
Amplitude and mass
What kind of collision takes place between the main platter and auxiliary platter?
An inelastic collision because the kinetic energy is not conserved.
Is angular momentum conserved?
Angular momentum is conserved in a system provided that the net torque of all external forces is zero L initial=L final L=Iω
What will happen to the period as the length of the pendulum increased?
As the length of the period increases, the length of the string increases. T and L are directly proportional
For which type of friction are we attempting to compensate when we add clay.
Kinetic friction because it slows the system down.
According to the theory, how should the accelerations of the two balls compare with each other?
Neglecting air resistance, the acceleration of the two balls should be the same because all objects on earth are subject to the force of gravity
Based solely on the angular speed vs. time graph, is the total mechanical energy of the platter/mass system conserved?
No
Does the mass return to its initial height above the floor at time t2
No
Based on the data, does the mass of the box affect the coefficient of friction?
No because the coefficient of static friction is unique to each surface and does not change with mass.
Does surface area affect the coefficient of friction?
No because there is no value in the formula that takes into account surface area.
A specific pendulum has a period of T, given by the equation above. IF the angle is increased from 2 degrees to 4 degrees, the period will
Remain the same
A specific pendulum has a period of T, given by the equation above. IF the mass of the pendulum, m, is decreased, the period will
Remain the same
The frictional force that holds an object in place is called ______ friction.
Static
What would happen to the system if you added clay until it moved on its own?
Static friction would be compensated for and it would speed the system up
Given the equation above, describe the graph that you would obtain if you plotted acceleration vs. the mass ratio. (see equation in quiz 6)
Straight line through the origin
Use the equation and picture above to answer the questions in this quiz. A specifc pendulum has a period of T, given by the equation above. IF the length of the string, L, is increased, the period will
T=2π√L/G Increase
The total angular momentum of a system of rotating objects is conserved if the vector sum of the torques of all the external forces acting on the system is zero.
True
Compare the accelerations of the two balls. Do they fall nearly the same acceleration?
Use percent difference Difference/average Difference is from experimental error
Compare the values of the acceleration to the predicted acceleration (g= 9.8 m/s2)
Use percent error experimental-actual/actual
If there acceleration is constant what should the velocity vs. time graph look like
Velocity vs. time data should lie along a line.
What can we obtain from knowing the slope?
We can find the magnitude of the acceleration
Falling Bodies Predictions
-Objects falling through air will have a constant positive acceleration -The acceleration is the same no matter the mass of the object. -A plot of their position vs. time squared will be a straight line through the origin with a slope equal to half of the acceleration due to gravity.
Is the period of the pendulum dependent upon the mass of the pendulum?
It is independent of the mass.
Units for angular momentum
kg×m/s2 L=Iω
When the pendulum is displaced from its equilibrium position, there is a restoring force that drives it back to the equilibrium
-The pendulum is said to undergo simple harmonic motion and will oscillate about its equilibrium position. -
Given the kinematics equation for the motion of an object falling from rest, x=.5g*t2), what kind of relationship is predicted between x and t? (select all that apply)
-displacement, x, and time, t, obey a power law. -x=k*t2, where k is a constant. -diplacement, x, is proportional to the square of the time, t2.
Kinetic engy
KE=1/2mv2 where v=rω ω is from information
If you plotted x vs. t2, for an object falling from rest (assuming down to be positive), what should the graph look like?
-positive slope -y-intercept is zero (goes through origin) -straight line
Based on the expression and the predicted relationship, what is the magnitude of the acceleration of each ball?
2 × slope (from graph)
The frictional force that slows an object down while in motion is called ______ friction.
Kinetic
What is the specific functional relationship?
D=.95(ft/s2)t2 (Slope)
From Newton's 2nd Law - If we plot acceleration vs. mass ratio what should our data look like? What is the slope?
Data should lie along a line w/ little scatter and the line of best fit should go near the origin. The slope should be gravity
A specifc pendulum has a period of T, given by the equation above. IF the pendulum is moved from the earth where the g is 9/8 m/s2, to Jupiter where it is 26.0 m/s2, the period of the pendulum will
Decrease
Velocity versus time
Direction-Positive (above the t-axis) Velocity- Increasing (Moving away from the t-axis) Acceleration- (Slope is positive and constant
Direction for position versus time graph
Direction-positive Velocity-Increasing Accelleration -positive
Refer to the graph of rotational speed vs. time for the platter/mass system to answer the questions 1-4 in this quiz. The Gravitational Potential Energy of the mass m at time t1 is _____________ the gravitational potential energy of the mass m at time t3.
Equal to
The coefficient of friction can be zero, meaning there is no friction between the two surfaces.
False
How well does the value for acceleration due to gravity agree with the theoretical value?
Find percent error Actual-theoretical/Actual
Gravitational Potential Energy
GPE=mgHinitial
The translational kinetic energy of the mass m and the rotational kinetic energy of the platter at time t1 is _________________ the translational kinetic energy of the mass m and the rotational kinetic energy of the platter at time t3.
Greater than
What will happen to the period of the pendulum as the displacement of the pendulum is increased.
It will remain the same because it is independent of the displacement because θ is too small and remains constant
What will happen to the period of pendulum as the mass is increased?
It will remain the same because the period is dependent upon the length of the string
How is the distance related to the time squared?
The distance is directly proportional to the time squared. D=kt2
Compare your three values for the coefficients of static friction (felt, cork, and plastic). What does this tell you about the relationship between the three surfaces
The rougher the surface, the greater the coefficient. Cork has the highest friction
According to the predicted relationship, how are the slopes of the graphs related to the motion of the balls (lab 3 falling bodies)
The slope is half of the acelleration due to gravity acting on the ball
Compare the two values for the coefficient of friction for felt (kinetic and static). What does this tell you about the relationship between the forces of static and kinetic friction.
The static friction is greater than kinetic because it must overcome it before it can move.
Why is there a decrease in rotational kinetic energy
There is friction. Energy is lost to heat and sound
If you drop a feather and penny in a vacuum ( no resistance), which one would hit the ground first?
They will hit at the same time.
Specific factors might explain why the total mechanical energy of the main platter and hanging mass are not conserved
Torque from friction and drag
What do you think will happen if you now reverse which mass is falling (friction rider is on the mass that is rising not falling
We would add the friction to the opposite side than the acceleration due to gravity. The weight will stop. Once the force is used up, the mass stops falling. Instead of compesating for friction, we are doubling the amount of friction on the system.
Is mechanical energy conserved?
Yes.Rotational Kinetic Energy-Mechanical Energy is still conserved provided that non-conservative forces do no net work. Mechanical Energy=GPE+KE+RKE (1/2 Iω↑2)
Considering our pulley system with a mass falling at a constant acceleration, what should the general shape of its position vs. time graph look like.
a curve with an increasing slope
How is distance related to time
distance and the time have a power relationship. -The exponent is positive -D=ktn, for n>1
Compare the maximum angular velocity for the three runs
v=rω As you increase the moment of inertia, there will be a decrease in angular velocity. CHECK!!!
According to kinematics (x=.5g*t2), the acceleration is dependant only upon
where the object is located.
