phys 2108 final

If a bus you are riding is traveling at a constant speed and then stops suddenly, you feel "thrown" forward. Which of the following is true at the instant the bus begins to stop? Assume the seat is frictionless and that you are not wearing a seatbelt.

You slide forward on the frictionless seat at the same velocity that the bus was traveling prior to the stop.

If we create a plot of wavelength vs inverse frequency, what will the value of the slope of a linear best fit line be equal to in terms of the tension of the string, T, and the linear mass density of the string, μ?

(t/mu)^0.5

Compute the torque (in m-N) applied by a hanging mass of 105.7 g at 37.8 cm away from the axle. The torque is applied perpendicularly to the radius.

0.392

A mass on a spring oscillates with a certain amplitude and a certain period T. If the mass is doubled, the spring constant of the spring is doubled, and the amplitude of motion is doubled, the period:

stays the same

Calculate the kinetic energy (in J) of a cart with mass 0.4960 kg travelling at a velocity of 0.48 m/s.

0.057

You measure a sheet of paper. The width is 8.46 inches and the length is 11.12 inches. What is the area of the paper in MKS units (m2)?

0.0607

The speed of light is 299,792,458 m/s. However, most physicists round this number to 3x108 m/s. What is the percent difference in these values using the correct number of significant digits? Assume the exact speed of light is the reference value.

0.07

In lab, you performed an experiment with a spring to find the mass of an "unknown mass." If the spring constant is 9.33 N/m and the "unknown mass" caused a displacement of \Delta 17.8 cm, what is the mass of the "unknown mass" in kg?

0.169

Calculate the momentum (in kg-m/s) of a cart with mass 0.4999 kg travelling at a velocity of 0.49 m/s.

0.24

A light ball collides head-on with a stationary heavy target elastically. The ball:

bounces backward

t/f The spin-mill should be high enough that it collides with the photogate head as it spins.

false

A 11600 kg railroad car is coasting on a level, frictionless track at a speed of 16.0 m/s when a 5420 kg load is dropped onto it. If the load is initially at rest, find the new speed of the car and the % change of the kinetic energy.

final speed 10.9 m/s change in ke = -31.84 %

in lab 6 you will use

inclinometer photogates triple beam balance

what instruments were used in week 5?

inclinometer triple beam balance meterstick force sensor

in this lab (and others) we will be doing calculations with the gravitational constant g = 9.8 m/s2. Because we will treat it as a mathematical constant assumed to be known exactly, how many significant digits does it contain?

infinite digits of precision and infinite sig digits

Using Hooke's Law, you find the spring constant of a given spring to be 8.9 N/m \pm 0.6 N/m. Your lab partner uses simple harmonic motion and finds the spring constant to be 7.9 N/m \pm 0.5 N/m. Would you consider these two springs to have the same spring constant?

yes

You measured the length, diameter and mass of two different cylinders. In both cases, you found that the length had 3 significant figures and that length was the measurement with the fewest number of significant digits. If you found the weight densities to be 38123 N/m3 and 38091 N/m3 and you round these values to the correct number of significant figures, can you conclude the two cylinders are made of the same material (do they have the same weight density)?

yes

Which of the following are valid reasons to take multiple measurements?

you gain precision and decrease the amount of uncertainty

Calculate the % change from before to after a collision if Pbefore = 0.178 and Pafter = 0.159.

-10.6

Using the pulley system below, if m1=1.8 kg and m2 = 5.4 kg, what is the acceleration of m2 in m/s/s? Use up as the positive direction for m2.

-4.9

In a new lab experiment, you find the spring constant of a "good" and "bad" spring. The "bad" spring is exactly the same as the "good" spring, except that it has been permanently deformed by misuse. If you find the "good" spring to have a spring constant of 9.92 N/m and the "bad" spring to have a spring constant of 4.00 N/m, what was the percent change in the spring constant caused by deforming the spring?

-59.68

If we create a plot of wavelength vs inverse frequency, what will the value of the y-intercept of a linear best fit line be equal to in terms of the tension of the string, T, and the linear mass density of the string, μ?

0

Calculate the potential energy stored in a cart of mass 497.0 g elevated to a height of 20.11 cm. Your result should be reported in Joules.

0.98

If the leftover energy in the previous problem is 176.3 J (it's not, don't go back and try to use this value) and the mass is 2 kg, what speed (in m/s) does the block have at the bottom of its slide? Revisit the definition of KE if needed.

13.28

A car moving at some speed hits the brakes and skids to a stop after 13 m on a level road. If the coefficient of friction for the road conditions of dry concrete is 0.74, what was the car's original speed (in m/s) before braking?

13.73

Recall that weight is a force and is equal to m*g, where g is the acceleration due to gravity exerted by the Earth near the Earth's surface. The acceleration due to gravity exerted by the moon near the moon's surface is 16.6% that of Earth. What is the weight (in N) of a person with a mass of 82.5 kg on the moon?

134.211

Momentum is defined as mass times velocity. You find the mass of a car to be 2123.6 kg and the velocity of the car to be 6.45 m/s, giving you a momentum of 13697.22 kg-m/s. Round this momentum to the correct number of significant digits.

13700

Calculate the spring constant, k, if the spring is compressed by 1.00 cm and the total stored potential energy is 0.00729 J. Your answer should be in N/m or kg/s2.

145.8

Calculate the work done on a cart (in Joules) by pulling it a distance of 87.6 cm with a force of 17.43 N parallel to the direction of travel.

15.27

A block of mass m begins at rest at the top of a ramp at elevation h with whatever PE is associated with that height. The block slides down the ramp over a distance d until it reaches the bottom of the ramp. How much of its original total energy (in J) survives as KE when it reaches the ground? (In other words, the acceleration is not zero like it was in lab and friction does not remove 100% of the original PE. How much of that original energy is left over after the friction does work to remove some?) m = 3.7 kg h = 6.1 m d = 5 m μ = 0.3 θ = 36.87°

177.67

A fighter pilot is exposed to an acceleration of 3g in the horizontal direction during takeoff. Knowing that 1g=9.8 m/s2 and that the mass of the fighter pilot is 60.4 kg, what force (in Newtons) does the fighter pilot experience in the horizontal direction? This is the force that she feels "pressing her into the back of the seat."

1775.76

How many consecutive periods will you measure for each run in the Simple Harmonic Motion experiment?

20

To leave Nicholson, you exit via the door to the quad. The door is 40 inches wide and has a mass of 200 kg. You push the door with a perpendicular force of 47.13N exactly 0.94m away from the hinge. This generates the minimum torque, \tau_1, required to open the door. If you pushed the door 0.22m away from the hinge, with what force (in N) must you push the door to supply the same torque?

201.37

Humans life an average of 79.8 years in the United States. Express this time in units of days if the conversion factor is exactly 365.25 days. Round your answer to the correct number of significant digits as given by the original time in years (because the conversion factor is known *exactly,* meaning to infinite precision).

29100

How many significant digits are in this number? 186000

3

The known area of a table is 1.50 m2. You measure the length of the table to be 1.26 m and the width to be 1.15 m. What is the percent error between the known area of the table and the measured area of the table you calculate using A = L*W?

3.4

If gas costs $1.98 per gallon, and it takes 21 seconds to pump one gallon of gas, how long will it take to pump $28.49 worth of gas (in seconds)?

302

You are swinging a yo-yo around in a circle above your head. Assume this is a perfect system: the mass of the string is negligible, the yo-yo is a point mass and your arm is a perfectly vertical axis of rotation. Given the mass of the yo-yo is m and the length of the string (radius of the circle traced by the yo-yo) is L, you find the moment of inertia to be I. If you double the length of the string, what is the new moment of inertia? Hint: Consider the equation for moment of inertia of a point mass about an axis in your lab manual.

4 /

You perform the Hooke's Law experiment and create a plot of Displacement vs. Force. You add a linear fit and find the following equation for the line: y=0.247 x - 0.015 What is the spring constant, k (in N/m or kg/s2)?

4.05

You perform the Simple Harmonic Motion experiment and create a plot of Period-Squared vs. Mass. You add a linear fit and find the following equation of the line: y=9.06x-0.087 What is the spring constant, k (in N/m or kg/s2)?

4.36

Find the percentage of the total work lost to friction if 27.1 J of work is put into pushing a block up a ramp resulting in 14.1 J of stored potential energy at the top. Report the percentage lost as a positive number.

47.97

If we create a plot of T^2 vs mass, what will the value of the slope of a linear best fit line be equal to?

4pi^2/k

One example of tolerance "that matters in the real world" can be found in radiation oncology clinics. Physicians will prescribe some dose of radiation to a patient's tumor that must be delivered within a certain tolerance (or range of doses) in order to control the tumor. If a physician prescribes 54.0 Gy +/-2.00%, what is the maximum dose the patient can receive (in Gy)? Note: A Gy is measure of the amount of energy deposited per unit mass.

55.08

Your friend weighs 152.6 lbs. What is your friend's mass in MKS units (kg)? Assume g = 9.8 m/s^2 and 1 lb = 4.448 N and that both of these conversion factors are known *exactly* (for significant digits purposes).

69

You will collect acceleration data from how many positions for the adjustable masses on the spin-mill?

7

(a) How many nodes are in the standing wave pictured? (a) How many antinodes are in the standing wave pictured? (a) What harmonic is the standing wave pictured?

7 6 6

A billiard ball with mass 3.3 kg is shot due west at 8.6 m/s. The ball collides elastically with a second billiard ball, also of mass 3.3 kg. The second billiard ball travels due west, the same direction as the first billiard ball was traveling. Assuming a frictionless table, what is the magnitude of the final velocity of the second billiard ball in m/s due west?

8.6

In figure skating, a triple Axel is a jump in which the figure skater leaps into the air while facing forward, performs 3.5 revolutions, and then lands facing backwards. During the spin, the skater hugs his/her arms close to the body. Choose the answer that best explains WHY the figure skater does this. Think about the experiment you performed on the rotating stool.

Due to conservation of angular momentum, decreasing the effective radius of the figure skater by pulling in the arms increases the angular velocity of the figure skater. This allows the figure skater to spin faster in the air to fully complete the triple Axel.

A mass is oscillating back and forth on a spring without friction, as shown. At which position is the magnitude of the acceleration of the mass a maximum? Position 0 is the relaxed (unstretched) position of the mass.

E

If the amplitude setting on the function generator is set too high, which of the following is true? (Select all that apply.)

It will be indicated by a pounding sound. The amplitude should be lowered immediately.

flip high, low

The picture below represents accuracy and precision.

What instruments will you be using week 7?

b. Triple-beam balance Correct c. Photogate Correct d. Mass Hanger Pan Correct

An ideal spring should behave in its relationship between force and displacement.

linearly

Sound is this type of wave.

longitudinal

vectors have :

magnitude and direction

Find the magnitude and direction of a vector with the following x- and y-components. Keep a few digits for the result to make sense, but not too many that we're overconfident. \vec{v}_x = 5N \vec{v}_y = 30N

magnitude: 30.41 N direction 80.58 degrees from the +x-axis

You measure the masses of four bricks to be: {3.4 kg, 3.5 kg, 3.6 kg, 4.2 kg}. What is the mean and standard deviation?

mean 3.7 stdev 0.36

All waves that cause particles of a material to be disturbed and transfer the disturbance to the neighboring particles by contact are this kind of wave.

mechanical

in lab 9 we used

mechanical vibrator electronic function generator string

Which of the following instruments will you be using to make measurements in lab 2? (Select all that apply.)

meter stick triple beam balance digital caliper

In an inelastic collision, which are conserved?

momentum

In general, how should you shuffle the mass in a rotating object to decrease its overall moment of inertia?

move mass closer to the axis of rotation

What are the units of k?

n/m

Does setting up a best fit line mean "connecting the dots"?

no

Two students measure the strength of a certain magnetic field to have the following values: Student A: 1.32 ± 0.01 T Student B: 1.37 ± 0.03 T Do the two students agree for the strength of the magnetic field?

no

You conduct an experiment like we did in lab to measure the mass of a textbook to be 1.319 +or- 0.006 kg . If Sarah measured it with a balance and obtained 1.308 kg, do these two measurements agree?

no

Imagine you have a system of two buckets as shown below. The buckets are spinning about an axle with frictionless bearings at some angular velocity, \omega. It starts to rain. What happens to the two-bucket system? Think about angular momentum.

omega must decrease to conserve angular momentum because because the rain increases the mass of the system (which increases the moment of inertia)

If I want to compare values before and after an event, I would use:

percent change

If I want to compare two separate values, I would use:

percent difference

If I want to compare predicted results to my measured results, I would use:

percent error

what instruments will you use in lab 4

pulleys slotted masses mass hanger pans force table

In MKS units, final answers of time should always be given in which of the following units?

seconds

For this week's experiment, n equals the following. (Select all that apply.)

the number of half wavelengths in the standing wave the number of antinodes in the standing wave

You perform an experiment in slacking off at work by clocking out earlier each week and seeing how it affects your paycheck. Properly title the graph and label the axes for the plot your collected data.

title: pay received vs time worked y axis: pay received ($) x axis: time worked (hours)

In the Simple Harmonic Motion experiment's Analysis, you will make a graph to determine the spring constant from your period measurements. Correctly title the graph and label (with units) the variables you will plot on the x- and y-axes.

title: period squared vs mass y: period squared (S^2) x:mass (kg)

You will end up plotting a graph to determine the value of the adjustable masses on the spin-mill. Set up and label the graph including units.

title: torque/angular acceleration vs radius y: t/a (kg-m^2) x: R(m)

This week, in Analysis, you will make a graph that you will use to determine the wave velocity. On the plot below, correctly select the title of the graph and the labels and units of the variables you will plot on the x- and y-axes.

title: wavelength vs 1/f y: wavelength (m) x: 1/f (s)

In this type of wave, the oscillation is perpendicular to the direction of the wave.

transverse

in lab 8 we used

triple beam balance stopwatch jolly balance

t/f You should unhook the alligator clip before you add additional mass to the mass hanger and reattach the clip afterward.

true

Break this vector into x- and y- components. Keep 5 decimal places of precision. \vec{v} = 15N \theta = 30 ^{\circ}

v(x)=12.99038N v(y)=7.5 N

Suppose we want to linearize by substitution the formula for dependent variable Kinetic Energy (K) with independent variable velocity (v). If the original equation is K=(1/2)mv^2, what will our "new" independent variable (x) be when we "map" this onto y = mx + b?

v^2

Consider the following picture.(flip) (a) What is the least-count of the ruler? 0.1 cm (b) From the picture, what is the measured value? (Use the correct number of significant digits and interpolate if necessary.) 10.5 cm

what is least count & what is the measured value?