physics 6B

An L-shaped container is filled with a stationary liquid. The space above the liquid surface at point C is at a pressure of 0.30 atm and only the liquid surface at bottom right is open to the outside air at 1.0 atm = 1.0 x 105 N/m2.  Use g = 10 m/s2.  The density of the liquid is ______ kg/m3.

Pc+pgh=Patm+pghatm

Block A weighs 15 N and has an apparent weight of 9 N when completely submerged in an ideal fluid. Block B weighs 20 N and has an apparent weight of 16 N when completely submerged in the same ideal fluid. The ratio of the densities ρA / ρB equals:

(Wa*Vb)/(Wb*Va)

Block A weighs 15 N and has an apparent weight of 9 N when completely submerged in an ideal fluid. Block B weighs 20 N and has an apparent weight of 16 N when completely submerged in the same ideal fluid. The ratio of the volumes VA / VB equals:

Vb/Va

If our atmosphere had a uniform density of 1.25 kg/m3 all the way up to a border with empty space above, that border would be ______ km above sea level.  The pressure at sea level is 1 atm = 105 N/m2 and g = 10 m/s2.  Enter your answer as an integer.

h=P/pg

An open container of water is filled to the very top. When a block with a density between 500 – 700 kg/m3 is gently placed in the container and floats (does not touch the bottom), it is observed that 2.5 liters of water flows over the edge of the container.  The mass of the block is ______ kg (1000 liters = 1 m3).

L*density

A rough model for our atmosphere is that the density of air is 1.14 kg/m3 and is uniform all the way up to a boundary with empty space above.  According to this model we would find a pressure of ____ atm at a height of 6.36 km above sea level.  The pressure at sea level is 1 atm = 105 N/m2 and g = 10 m/s2.

P=Po-pgh

A horizontal board of negligible thickness and area 1.0 m2 hangs from a spring scale that reads 70 N when a 4.0 m/s wind moves above the board. The air below the board is stationary. When the wind stops, the scale reads ______ N. The density of air is 1.25 kg/m3 and treat the air as an ideal fluid.

Change of P = Pbelow-Pabove=0.5pv²above

Flift=change of P*A

T+Flift=mg

An object accelerates downward at a constant rate of 2.0 m/s2 while completely submerged in water. Neglect the viscosity (fluid friction) of the water. The average density of the object is ______ kg/m3.  The density of water is 1000 kg/m3 and g = 10.0 m/s2

pobj=(pwaterg)/(g-a)

A hydraulic lift is made by sealing an ideal fluid inside a container with an input piston of cross-sectional area 0.006 m2, and an output piston of cross-sectional area 1.2 m2. The pistons can slide up or down without friction while keeping the fluid sealed inside.  The maximum weight that can be lifted when a force of 50 N is applied to the input piston is ______ N.

F2=F1(A2/A1)

An ideal fluid flows through a vertically oriented cylindrical tube of varying radius with cross-section shown. Point A is higher than point B, and B is higher than C. What can we conclude about the fluid speed at points A, B, and C?

Small> large

An ideal fluid flows through a vertically oriented cylindrical tube of varying radius with cross-section shown. Point A is higher than point B, and B is higher than C.  What can we conclude about the fluid pressure at points A, B, and C?

Big> small

An ideal horizontal spring-mass system oscillates with a period of 0.800 seconds. The mass is 3.00 kg but the spring constant is not known. When this same spring and mass are arranged to hang vertically, the frequency of oscillations will be ______ Hz. (answer with 3 sig figs)

f=1/T

An ideal horizontal spring-mass system oscillates with an amplitude of 0.200 m. The spring has constant 100 N/m and it’s observed that the mass is moving at 1.80 m/s when it is 0.100 m from its equilibrium position. As the mass oscillates, its maximum speed is ______ m/s.  (answer with 3 sig figs)

m=(k(A²-x²))\v²

vmax=sqrt(k/m)*A

An ideal horizontal spring-mass system oscillates with an amplitude of 0.200 m. The spring has constant 100 N/m and it’s observed that the mass is moving at 1.80 m/s when it is 0.100 m from its equilibrium position. As the mass oscillates, its maximum acceleration is ______ m/s2 .  (answer with 3 sig figs)

(k/m)=(v²)/(A²-x²)

a=k/m*A

An ideal horizontal spring-mass system oscillates with an amplitude of 0.200 m. The spring has constant 100 N/m and it’s observed that the mass is moving at 1.80 m/s when it is 0.100 m from its equilibrium position. As the mass oscillates, its period is ______ seconds. (answer with 3 sig figs)

w²=(k/m)=(v²/A²-x²)

T=2pi/w

An ideal vertical spring-mass system oscillates with a period of 1.60 second when the mass used is 2.00 kg. In its equilibrium position (when the net force on the mass is zero) the spring stores ______ J of potential energy.  Use g = 10 m/s2  (answer with 3 sig figs) /

k=(4pi²m)/T²

Us=(mg)²/2k

The pressure at a point 30 m below the surface of a freshwater lake at sea level is ______ atm.  Use g = 10.0 m/s2, density of water = 1000 kg/m3, and enter just 1 significant figure.

Phydro=pgh

ATM+atm

An ideal fluid flows through a vertically oriented cylindrical tube of varying radius with cross-section shown. Point C is higher than point B, and B is higher than A.  What can we conclude about the fluid speed at points A, B, and C

Small>big

An ideal fluid flows through a vertically oriented cylindrical tube of varying radius with cross-section shown. Point C is higher than point B, and B is higher than A.  What can we conclude about the fluid pressure at points A, B, and C?

More info needed

A simple pendulum is made my attaching a rod of negligible mass to a 2.0 kg pendulum bob at the end. It is observed that on Earth, the period of small-angle oscillations is 1.0 second. It is also observed that on Planet X this same pendulum has a period of 2.3 seconds. The pendulum bob has a weight of ______ N on Planet X.  Use g (on Earth) = 10.0 m/s2 and enter your answer with 2 significant figures.$^{\chi}$

gX=gE(TE/TX)²

w=mg

A simple pendulum is made my attaching a 1.9 m rod of negligible mass to a 1.5 kg pendulum bob at the end.  The period of small-angle oscillations for this simple pendulum is ____ seconds

T=2pisqrt(L/g)

Speakers C and D emit the same pure tone of wavelength 2.35 m, are exactly in phase, and are 5.15 m apart.  How many loud spots (completely constructive interference) exist along the line segment connecting the speakers?  Enter an integer.

-x←0→x

-wavelength←0→wavelength

Speakers C and D emit the same pure tone of wavelength 0.9 m, are exactly in phase, and are 5.6 m apart.  An observer begins at point P, equidistant to the two speakers, and moves directly to point Q along the path shown. Point Q is the position of the 1st loud spot (completely constructive interference) encountered after leaving point P. Point Q is ______ m further from D than from C.

Wavelength

Speakers C and D emit the same pure tone of wavelength 2.78 m, are exactly in phase, and are 5.21 m apart.  The shortest distance from either speaker to a loud spot (completely constructive interference) along the line segment connecting the speakers is ____ m.

mapart-2x=wavelength

Speakers C and D emit the same pure tone of wavelength 2.54 m, are exactly in phase, and are 8.51 m apart.  The shortest distance from either speaker to a quiet spot (completely destructive interference) along the line segment connecting the speakers is ____ m.

d/wavelength= y

m+0.5<y

M has to be whole #

Change of L=m+0.5*x

d-2X= change of L

Two speakers, 7.0 m apart, are in phase and emit a pure tone of wavelength 3.6 m.  The closest loud spot (completely constructive interference) to either speaker along a line segment connecting the speakers is ______ m away.

Change of r = m * wavelength

(d-x)-x=wavelength

Trucks 1 and 2 each have a siren emitting a pure tone of 900 Hz. Truck 1 remains stationary and truck 2 moves at 15.0 m/s away from the observer as shown in the diagram. The speed of sound is 340 m/s.  The observer must run at a speed of ______ m/s (along a line segment connecting the trucks, although direction right or left is not given) to make the observed beat frequency become zero?  Enter 3 significant figures.

vo=(v-vs)/(2v+vs)

Trucks 1 and 2 each have a siren emitting a pure tone of 900 Hz. Truck 1 remains stationary and truck 2 moves at 15.0 m/s away from the observer as shown in the diagram. The speed of sound is 340 m/s. The observer is stationary and observes a beat frequency of ______ Hz.  Enter 3 significant figures.

f2=fo(v/v+vs)

fbeat=|f1-f2|

Two speakers, 7.0 m apart, are in phase and emit a pure tone of wavelength 3.6 m.  There are a total of ______ quiet spots (completely destructive interference) along the line segment connecting the speakers?

change of r=(m+0.5)*wavelength

Guess m as whole numbers

Until change of r wont go over d

2x

Two speakers, 7.0 m apart, are in phase and emit a pure tone of wavelength 3.6 m.  The closest loud spot (completely constructive interference) to either speaker along a line segment connecting the speakers is ______ m away.

(d-x)-x=wavelength

When two closed tubes (closed at one end) of different lengths each resonate at their 3^rd harmonic, a 9 Hz beat frequency is observed.  Both tubes are now opened at both ends. When each tube now resonates at its 2^nd harmonic frequency, the observed beat frequency is ______ Hz./ /

f3,1=3v/4L

f2=2v/2L

f2/f3=(v/L)/(3v/4L)

A closed tube (closed at one end) of length L resonates at its 7th harmonic.  At which distance(s) from the open end is a pressure node found?  Select all that apply.

Wavelength= 4L/7

1 node=0+2L/7

2nd node= 2L/7+ 2L/7

3rd node= 4L/7+2L/7 etc

A tube closed at one end of length 1.40 m resonates at its 5th harmonic. Which of the following distances from the open end will a displacement node be found

L=(n*wavelength)/4

x2=wavelength/2

A guitar string, fixed at both ends, oscillates in its 3^rd harmonic standing wave mode. It is observed that the closest node to one of the fixed ends is 24 cm from the fixed end. The tension in the string is now increased by 44%while the mass and length of the string remain unchanged.  When the string now oscillates in its 6^th harmonic standing wave mode, the closest node to a fixed end is how far away?

d to closest node=L/n

d=L/n2

A tube closed at one end of length 1.67 m resonates at its 7^th harmonic. The closed end is ____ m away from the nearest pressure node.

L=n(wavelength/4)

A tube open at both ends of length 2.11 m resonates at its n = 3 harmonic. Either open end is ____ m away from the nearest displacement node.

L=n(wavelength/2)

Wavelength =2L/n

d=wavelength/4

A guitar string, fixed at both ends, oscillates in its 4th harmonic standing wave mode. It is observed that the closest node to one of the fixed ends is 15 cm from the fixed end. The tension in the string is now increased by 44% while the mass and length of the string remain unchanged.  When the string now oscillates in its 3rd harmonic standing wave mode, the closest node to a fixed end is how far away?

d=L/n

d2=L/n2

Two concentric conducting spherical shells each have a net charge of -1 C and all charges remain at rest. The charge on the inner surface of the outer shell is -1 C.  How much charge is suspended within the central cavity of the inner shell (not touching the inner shell)?

qcavity+net charge+outer shell=0

The electric field between the plates of an ideal parallel plate capacitor has magnitude 3000 V/m.  The change in potential energy of the system as a +2 C charge is moved from A to B is ______ J.

Change of U=q*change of V=q(E*change of y)

Two concentric conducting spherical shells each have a net charge of +1 C and all charges remain at rest. The charge on the outer surface of the outer shell is +1 C. The outer surface of the outer shell is at a potential of +2 V. The inner surface of the inner shell is at a potential of ______ V.

qenclosed=net+outer

qenclosed+potential= inner potential

When a proton is moved from point A to point B, the potential energy of the system increases by 3 eV. The potential at A is -3 V.  The potential at B is ______ V .

Pot energy+potential at A= B potential

When an electron is moved from point A to point B, the potential energy of the system increases by 2 eV. The potential at A is -2 V.  The potential at B is ______ V

Potential energy+B=A

+1.0 C of charge is at one corner of a square of side 0.50 m. -1.0 C is at an adjacent corner. The potential is chosen so that V approaches 0 very far from the charges.  The electrical potential energy in this system is ______ x 10¹⁰ J.

U=((8.99×10^9)(charge)(charge))/r

+1.0 C of charge is at one corner of a square of side 0.30 m. -1.0 C is at an adjacent corner. The potential is chosen so that V approaches 0 very far from the charges.  The potential at point A is ______ x 10⁹ V.

r=sqrt(r²+r²)

V=k(q1/r1+q2/r2)

Charges lie at the vertices of an octagon as shown. The integer values represent the number of Coulombs of charge at each location. The distance from each charge to the center is 0.10 m.  The potential is chosen so that V approaches 0 very far from the charges.  The potential at the center of the octagon is ______ x 10¹¹ V.

V=$\varepsilon$ (k*qi)/r

V=(k/r)$\varepsilon$ *qi

Eqi add up all corners

The potential at points A and B are: V_A = -2 V and V_B = 6 V. When a +5 C charge is moved from A to B, the change in potential energy of this system is ______ J.

Change of U=q(V2-V1)

When a 6 V battery is attached to a 3 F capacitor, the charge on the capacitor plates is 18 C.  When the battery is replaced with a 3 V battery, the capacitance of this capacitor is now ______ F.

3

The potential at the corner of a solid conducting cube of length 0.2 m is -4 Volts. The cube has a net charge of -8 C and all charges on the cube remain at rest. What is the potential at the center point of the cube?

-4

When a 3.1 V battery is attached to a capacitor, the charge on the capacitor plates is 15.1 C.  When the battery is replaced with a 13.2 V battery, the capacitance of this capacitor is now ______ F.

C=Q/V

The capacitors are initially uncharged.  When the switch is closed the battery releases ______ J of energy.

U=0.5CeqV²

A battery is discharging.  Electrons exit the battery through the ______ terminal, at a ______ potential than when they entered the battery.

Negative; higher

A steady flow of 3.7 A enters the negative terminal of a 11 V battery.  During a 3.8 second period, ____ C of charge exits the battery's positive terminal.

Q=I*t

A 4 V battery is attached to the capacitor network shown.  C₁= 3 F, C₂ = 1 F, and C₃ = 3 F.  The capacitors are initially uncharged.  When the switch is closed, the battery releases ______ J of energy.

1/Ceq

E=CeqV²

An incandescent light bulb has a power rating of 40 W when connected to a wall outlet of voltage 120 V. The resistance of the filament in the light bulb is ______ Ohms.

P=V²/R

R=V²/P

A 6 V battery attached to a resistor causes 2 A of current to flow through the resistor.  When the same resistor is attached to a 12 V battery instead, the resistance of the resistor is ______ Ohms.

R=V/I

A uniform cylinder with resistance R is cut in thirds lengthwise and the pieces are then attached as shown. Each piece has the same length as the original cylinder.  What is the equivalent resistance of this new combination?

R=p(L/A)

1/Req=1/Rtop+1/Rbottom

The capacitors are initially uncharged.  When the switch is closed the battery releases ______ J of energy.

Ceq=add middle and low F

Ebattery=QV²

U=0.5CV²

The power consumed by the 3 Ohm resistor is ______ W

Rp=(3×6)/(3+6)

Req=2+Rp

Itotal=V/Req

Vp=Itotal*Rp

P=V²/R

A battery has an EMF of 12 Volts, internal resistance of 0.5 Ohms, and its terminal voltage is measured to be 13 Volts. The battery is ________ and has a current of ____ Amps passing through.

Battery is charging since 13>12

V=EMF+I*r (Would be -I*r if discharging)

The voltage across the 6 Ohm resistor is ______ Volts.

I=V/Rtotal

V=I*R

Vparallel=Vbattery-V

The 12 Volt battery releases ______ Watts of power

1/Rp=1/€+1/€

Rtotal=other € +Rp

P=V²/Rtotal

A battery is discharging.  Electric current exits the battery through the ______ terminal, at a ______ potential than when it entered.

Positive; higher

A battery and light bulb (shown as a resistor) are arranged in the circuit on the left. In order to measure the voltage across the bulb and the current through the bulb without affecting the brightness of the bulb, an ideal voltmeter should be placed at point ____ , and an ideal ammeter may be placed at point ____ .  (Choose any correct set to receive full credit)

Voltmeter: C, B

Ammeter=A, C