A series ac circuit consists of a voltage source of frequency f = 60 Hz and source voltage amplitude 345 volts, a resistor of resistance R = 255 Ω, a capacitor of capacitance C = 6.2×10−6F, and an inductor of inductance L.

(a) What must be the value of L for the phase angle Φ to be zero?

(b) When L has the value calculated in (a), what is the current amplitude in the circuit?

A wagon is rolling forward on level ground. Friction is negligible. The person sitting in the wagon is holding a rock. The total mass of the wagon, rider, and rock is 98.9 kg. The mass of the rock is 0.291 kg. Initially the wagon is rolling forward at a speed of 0.490 m/s. Then the person throws the rock with a speed of 16.1 m/s. Both speeds are relative to the ground. Find the speed of the wagon after the rock is thrown (a) directly forward in one case and (b) directly backward in another.

A copper collar is to fit tightly about a steel shaft whose diameter is 7.0000 cm at 20° C. The inside diameter of the copper collar at that temperature is 6.9760 cm. After the collar is heated and fitted about the steel shaft, it begins to cool. What is the tensile stress in the copper collar when its temperature returns to 20° C?

____________________N/m2

A vertical spring (ignore its mass), whose spring constant is 825 N/m , is attached to a table and is compressed down by 0.160 m.

A)What upward speed can it give to a 0.360-kg ball when released? Express your answer to three significant figures and include the appropriate units.

B) How high above its original position (spring compressed) will the ball fly? Express your answer to three significant figures and include the appropriate units.

A 123 turn circular coil of radius 2.27 cm is immersed in a uniform magnetic field that is perpendicular to the plane of the coil. Over an interval of 0.167 s , the magnetic field strength increases from 54.5 mT to 94.1 mT . Find the magnitude of the average emf avg induced in the coil during this time interval, in millivolts.

A 45.0-g object connected to a spring with a force constant of 50.0 N/m oscillates with an amplitude of 7.00 cm on a frictionless, horizontal surface.

(a) Find the total energy of the system.

(b) Find the speed of the object when its position is 1.30 cm. (Let 0 cm be the position of equilibrium.)

(c) Find the kinetic energy when its position is 3.50 cm.

(d) Find the potential energy when its position is 3.50 cm.

A railroad car of mass 3.10 ✕ 10^4 kg moving at 3.50 m/s collides and couples with two coupled railroad cars, each of the same mass as the single car and moving in the same direction at 1.20 m/s.

(a) What is the speed of the three coupled cars after the collision?

__m/s

(b) How much kinetic energy is lost in the collision?

__J

The Photoelectric Effect Lab 10

Prelab Questions : Predictions

1. If the light shining on the metal becomes brighter, will the kinetic energy of the emitted electrons increase?

2. If the light shining on the metal becomes brighter, will the number of electrons being emitted per second (the photo-current) increase?

3. If the frequency of the light shining on the metal is increased, will the number of electrons being emitted per second (the photo-current) increase?

4. If the frequency of the light shining on the metal is increased, will the kinetic energy of electrons being emitted increase?

5. Will all colors (frequencies) of light cause electrons to be emitted by the metal? What is the condition on wavelength for Potassium that light should cause electrons to be ejected?

5. If light with the same frequency and same power shines on two different metals with different work functions, will both metals emit electrons?
   1. Will these electrons have the same kinetic energy?
   2. Will the photo-current be larger for the metal with the smaller work function?

(1) Parasaurolophus was a dinosaur whose distinguishing feature was a hollow crest on the head. The 1.2m long hollow tube in the crest had connections to the nose and throat, leading some investigators to hypothesize that the tube was a resonant chamber for vocalization. (Figure 1)

If you model the tube as an open-closed system, what are the first three resonant frequencies? (Use 350 m/s for the speed of sound.)

Enter your answers using two significant figures in ascending order separated by commas.

(2) Tendons are, essentially, elastic cords stretched between two fixed ends; as such, they can support standing waves. These resonances can be undesirable. The Achilles tendon connects the heel with a muscle in the calf. A woman has a 20-cm-long tendon with a cross-section area of 120mm2. The density of tendon tissue is 1100 kg/m3.

For a reasonable tension of 600N , what will be the fundamental resonant frequency of her Achilles tendon?

Express your answer to two significant figures and include the appropriate units.

1.) A hiker, who weighs 860 N, is strolling through the woods and crosses a small horizontal bridge. The bridge is uniform, weighs 3220 N, and rests on two concrete supports, one on each end. He stops 1/4 of the way along the bridge. What is the magnitude of the force that a concrete support exerts on the bridge (a) at the near end and (b) at the far end?

2.) A jet transport has a weight of 1.09 x 106 N and is at rest on the runway. The two rear wheels are 17.0 m behind the front wheel, and the plane's center of gravity is 11.2 m behind the front wheel. Determine the normal force exerted by the ground on (a) the front wheel and on (b) each of the two rear wheels.

3.) A clay vase on a potter's wheel experiences an angular acceleration of 8.38 rad/s² due to the application of a 18.5-N m net torque. Find the total moment of inertia of the vase and potter's wheel.

Describe an experiment to determine if a resistor models ohms law.

(i) Draw a diagram of the experimental setup. Label all the measured quantities and draw or state what equipment is used.

(ii) Describe the overall procedure including any necessary steps to reduce experimental uncertainty. It should be thorough enough so that another lab student can follow the directions.

What the physics behind a Ballista?

Steve Young stands on the 20-yard line, poised to throw long. He throws the ball at initial velocity v0 equal to 15.4 m/s and releases it at an angle θ equal to 45.0∘ .

1) Having faked an end around, Jerry Rice comes racing past Steve at a constant velocity VJ equal to 8.00 m/s, heading straight down the field. Assuming that Jerry catches the ball at the same height above the ground that Steve throws it, how long must Steve wait to throw, after Jerry goes past, so that the ball falls directly into Jerry's hands? (Express your answer to three significant figures.)

2) Jerry is coming straight past Steve at VJ equal to 8.00 m/s. But just as Jerry goes past, Steve starts to run in the same direction as Jerry with VS equal to 1.40 m/s. How long must Steve wait to release the ball so that it falls directly into Jerry's hands? (Express your answer to three significant figures.)

A fugitive tries to hop on a freight train traveling at a constant speed of 5.0 m/s. Just as an empty box car passes him, the fugitive starts from rest and accelerates at a = 4.0 m/s²to his maximum speed of 8 m/s.

(a) How long does it take him to catch up to the empty box car?
_____________ s

(b) What is the distance traveled to reach the box car?
_____________ m

You are standing at x=8.0km and your assistant is standing at x=5.0km. Lightning bolt 1 strikes at x=0km and lightning bolt 2 strikes at x=14.0km. You see the flash from bolt 2 at t=20μs and the flash from bolt 1 at t=51μs.

If not, what was the time difference between the two?