The water level in a vertical glass tube 1.00 m long can be adjusted to any position in the tube. A tuning fork vibrating at 716 Hz is held just over the open top end of the tube, to set up a standing wave of sound in the air-filled top portion of the tube. (That air-filled top portion acts as a tube with one end closed and the other end open.) take the speed of sound to be 343 m/s. a) for how many different positions of the water level will sound from the fork set up a resonance in the tube's air-filled portion? What are the b) least and c) second least water height in the tube for resonance to occur?

Multiple choice: The presence of a black hole in a galaxy core can be inferred from (a) the total mass of the galaxy; (b) the speeds of stars near the core; (c) the color of the galaxy; (d) the distance of the galaxy from the Milky Way Galaxy; or (e) the diminished brightness of starlight in the galaxy core, relative to surrounding areas.

Multiple choice: Which one of the following statements about black holes is false? (a) Inside a black hole, matter is thought to consist primarily of iron, the endpoint of nuclear fusion in massive stars. (b) Photons escaping from the vicinity of (but not inside) a black hole lose energy, yet still, travel at the speed of light. (c) Near the event horizon of a small black hole (mass = a few solar masses), tidal forces stretch objects apart. (d) A black hole that has reached an equilibrium configuration can be described entirely by its mass, electric charge, and amount of spin (“angular momentum”). (e) A black hole has an “event horizon” from which no light can escape, according to classical (i.e., non-quantum) ideas.

Multiple choice: Which one of the following statements about black holes is true? (a) The surface of the singularity of a black hole is known as the event horizon. (b) Being more massive, a supermassive black hole has a greater gravitational pull than a stellar-mass black hole, so if you approach the event horizon of a supermassive black hole, you will be torn apart more easily than if you approach the event horizon of a stellar-mass black hole. (c) If the Sun were to become a black hole of the same mass, Earth would spiral into the black hole and be eaten. (d) The “photon sphere” is a region inside a black hole where photons orbit the center, so they cannot escape. (e) In principle, energy can be extracted from a region outside a rotating black hole.

Multiple choice: Which one of the following statements about the detection (or potential detection) of black holes is false? (a) Black holes cannot be detected because they emit no light and are therefore impossible to directly observe. (b) A binary pair of black holes was recently detected through measurements of the gravitational waves emitted when they merged to form a single black hole. (c) The presence of supermassive black holes in the centers of galaxies has been inferred from the motions of stars and gas near them. (d) Evidence for black holes can be found if material in the surrounding accretion disk goes through the event horizon and fades from view, rather than releasing energy as it hits a hard stellar surface. (e) Candidate black holes are sometimes found in binary systems that suddenly brighten at X-ray wavelengths.

A 2·g spider is dangling at the end of a silk thread. You can make the spider bounce up and down on the thread by tapping lightly on its feet with a pencil. You discover that you can give the spider the largest amplitude on the thread by tapping exactly once every second. (a) What is the spring constant of the silk thread? N/m (b) After further experimentation, you discover that if you tap at a rate of three times every two seconds, the amplitude is 20% of its maximum value. What is the damping constant for the thread? kg/s

The figure shows a pendulum of length L = 2.6 m. Its bob (which effectively has all the mass) has speed v₀ when the cord makes an angle θ₀ = 42° with the vertical. (a) What is the speed of the bob when it is in its lowest position if v₀ = 9.1 m/s? What is the least value that v₀ can have if the pendulum is to swing down and then up (b) to a horizontal position, and (c) to a vertical position with the cord remaining straight? (d) Do the answers to (b) and (c) increase, decrease, or remain the same if θ₀ is increased by a few degrees?

A 0.30 kg puck, initially at rest on a frictionless horizontal surface, is struck by a 0.20 kg puck that is initially moving along the x axis with a velocity of 2.4 m/s. After the collision, the 0.20 kg puck has a speed of 0.8 m/s at an angle of θ = 53° to the positive x axis.

(a) Determine the velocity of the 0.30 kg puck after the collision.
_ at _ ° from +x axis

(b) This was a(n) _ collision since K_f(No Response) K_i

A rescue plane flies horizontally at a constant speed searching for a disabled boat. When the plane is directly above the boat, the boat's crew blows a loud horn. By the time the plane's sound detector receives the horn's sound, the plane has traveled a distance equal to one-third its altitude above the ocean. Assuming it takes the sound 2.02 s to reach the plane, and taking the speed of sound to be 343 m/s, determine the following.

(a) the speed of the plane
m/s

(b) the altitude of the plane
m

A uniform hoop (I = MR2), solid disk (I = 1/2 MR2), and solid sphere (I = 2/5 MR2), each with the same mass and radius, are rolling without slipping, at the same speed on a horizontal surface. The surface they’re rolling on then begins to angle upward. Which of the three objects rolls the least distance up the inclined plane (still assuming that the objects do not slip)?

A The question cannot be answer unless the slope of the inclined plane is known.

B They all go the same distance

C The solid disk

D The hoop

E The solid sphere

1. The angle of an airplane propeller makes with the horizontal as a function of time is given by θ=(125rad/s)t+(42.5rad/s^2)t^2. estimate the instantaneous angular velocity at t=0.00s by calculating the average angular velocity from t=0.00s to t=0.010s

A. Estimate the angular speed at t = 0 by calculating the average angular speed between ti = 0 and tf = 0s.

B. Estimate the angular speed at t = 1.00 by calculating the average angular speed between ti = 1.00 and tf = 1.01s.

C. Estimate the angular speed at t = 2.00 by calculating the average angular speed between ti = 2.00 and tf = 2.01s.

D. Based on the above calculations, is the angular acceleration of the propeller negative, zero, or positive? Explain.

E. Calculate the average angular acceleration from t = 0.00 to 1.00s and from t = 1.00 to 2.00s.

F. Compare the angular acceleration calculated in E with the value of angular acceleration observed in the appropriate coefficient of the original equation for angle as a function of time. If they are not the same, explain why this might be?

A fellow student with a mathematical bent tells you that the wave function of a traveling wave on a thin rope is y(x,t)=(2.30mm)cos[(6.18rad/m)x+(702rad/s)t]. Being more practical, you measure the rope to have a length of L and a mass of 0.00333 kg.

Part A Determine the amplitude. Express your answer with the appropriate units. A=

Part B Determine the frequency. Express your answer with the appropriate units. f=

Part C Determine the wavelength. Express your answer with the appropriate units. λ=

Part D Determine the wave speed. Express your answer with the appropriate units. v=

Part E Determine the direction the wave is traveling. Determine the direction the wave is traveling. −x−direction +x−direction

Part F Determine the tension in the rope. Express your answer with the appropriate units.

Part G Determine the average power transmitted by the wave. Express your answer with the appropriate units.

Two loudspeakers emit sound waves along the x-axis. A listener in front of both speakers hears a maximum sound intensity when speaker 2 is at the origin and speaker 1 is at x = 0.540m . If speaker 1 is slowly moved forward, the sound intensity decreases and then increases, reaching another maximum when speaker 1 is at x =0.930m .

What is the phase difference between the speakers?

How many 65-W lightbulbs can be connected in parallel across a potential difference of 80 V before the total current in the circuit exceeds 2.0 A ?

Does the sign of the charge of an elementary particle, like an electron or proton, is a more, or less, fundamental property than the "sign" of its symmetry?

REMARKS The negative value of q indicates the image is virtual, or behind the mirror. The image is upright because M is positive.

QUESTION Is the image that a convex mirror produces real or virtual?

The image is always real.It depends on the focal length of the mirror.    The image is always virtual.It depends on the distance to the object.

PRACTICE IT

Use the worked example above to help you solve this problem. An object 3.13 cm high is placed 20.1 cm from a convex mirror with a focal length of 7.70 cm.

(a) Find the position of the image.
cm

(b) Find the magnification of the mirror.


(c) Find the height of the image.
cm

EXERCISEHINTS:  GETTING STARTED  |  I'M STUCK!

Suppose the object is moved so it is 3.85 cm from the same mirror. Repeat parts (a) through (c).

(a) q =  cm

(b) M =

(c) h' =  cm

The image is  ---Select--- upright and virtual inverted and virtual inverted and real upright and real .

17.You launch a projectile at an initial speed of 45.8 m/s from the ground. After 3.30 seconds of flight, the projectile lands on the ground. At what angle above the horizontal was the projectile launched?

18.A projectile is fired from the ground, reaches a maximum height of 56.4 m and lands a distance of 39.0 m away from the launch point. What was the projectile s launch velocity?

Is our society truly facing an "energy crisis", assuming by this term we mean that we are running out of energy? What is happening to our energy resources as a result of the increasing industrialization of the world?