a. A relatively rare transition of the hydrogen atom emits a radio photon with with ? = 21 cm. This emission line is extremely important to astronomers for two main reasons: it cuts through most gas and dust without being absorbed and, although transition is rare, there is so much hydrogen in space that the 21 cm photons are themselves quite common. Suppose that one such photon from a distant galaxy is measured to have a wavelength of just 11 cm. How fast is that galaxy receding from us?

b. Assuming that the speed you found in problem a is enitrely due to cosmic expansion, how far away is the galaxy from us?

What is the diameter of Planet X in Earth diameters and in AU? (The diameter of Earth is 1.3 × 10⁷ m.)

A gun is placed on a cliff of height 60 m above ground level, and fires a projectile at an angle of 50 degrees. The muzzle velocity of the projectile is 139 m/s.

What will be the magnitude of the total velocity when it hits the level ground (y=0m).

Round your answer to the nearest tenth of m/s.

A uniform disk with radius 0.310 m and mass 30.0 kg rotates in a horizontal plane on a frictionless vertical axle that passes through the center of the disk. The angle through which the disk has turned varies with time according to ?(t)=( 1.10 rad/s)t+( 6.90 rad/s2 )t2

What is the resultant linear acceleration of a point on the rim of the disk at the instant when the disk has turned through 0.100 rev ?

Airplane travelers sometimes note that their cosmetics bottles and other containers have leaked during a flight. What might cause this? (b) When blood pressure is measured, why must the cuff be held at the level of the heart? (c) Why does buoyancy occur? Is buoyant force a conservative force? Is potential energy associated with it? Explain your answer. (d) Explain how the tube in the figure below, known as a siphon, can transfer liquid from one container to a lower one even though the liquid must flow uphill for part of its journey. (Note that the tube must be filled with water to start with.)

This table below provides approximate values for the intracellular and extracellular concentrations in unit mmol/L for sodium, potassium, and chlorine ions in a frog muscle with a resting potential difference of −98 mV and for the squid axon with a resting potential difference of −70 mV. Calculate the equilibrium potential difference (in mV) for each ion species in both cases at 17°C.

Table:

Frog muscle (intracellular, extracellular)

Na+ = 9-13, 120

K+ = 140, 2.5

Cl- = 3.5, 120

Squid Axon (intracellular, extracellular)

Na+ = 50, 440

K+ = 400, 20

Cl- = 40-100, 560

A 510-turn solenoid has a radius of 8.00 mm and an overall length of 14.0 cm. (a) What is its inductance? (b) If the solenoid is connected in series with a 2.50-?(ohm electrical symbol) resistor and a battery, what is the time constant of the circuit?

Radioactive Half Life of Barium-137m: Are the detected activity and actual activity of the source Identical? What difference would this make in the analysis of the data?

Ask Your Teacher A scale reads 344 N when a piece of nickel is hanging from it. What does it read (in N) when it is lowered so that the nickel is submerged in water Please help solve, I need help with how to calculate. Thank you

In an experiment designed to measure the speed of light, a laser is aimed at a mirror that is 47.5 km due north. A detector is placed 116 m due east of the laser. The mirror is to be aligned so that light from the laser reflects into the detector.

(a) When properly aligned, what angle should the normal to the surface of the mirror make with due south?

(b) Suppose the mirror is misaligned, so that the actual angle between the normal to the surface and due south is too large by 0.005

True or False

The magnetic field at a radial distance R from a current element i dl is a maximum when the current element direction is at right angles to the radial line.

Induced electric field lines are continuous, i.e. having no beginning or ending points.

An arbitary shaped Amperian loop through which no currents pass may itself pass through a magnetic field.

Induced electric field lines have a beginning and end point.

The negative sign in Faraday's Law (Lenz's Law) implies that the induced EMF is in opposition to any changes in magentic flux.

The current induced in a copper wire coil by a changing magnetic field is dependent of the number of turns in the coil.

The negative sign in Faraday's Law (Lenz's Law) implies that the induced EMF is in opposition to any changes in magentic flux.

A motorcycle is following a car that is traveling at constant speed on a straight highway. Initially, the car and the motorcycle are both traveling at the same speed of 18.0m/s , and the distance between them is 54.0m. (A) How long does it take from the moment when the motorcycle starts to accelerate until it catches up with the car? In other words, find t2-t1. (B) How far does the motorcycle travel from the moment it starts to accelerate (at time t1) until it catches up with the car (at time t2)? Should you need to use an answer from a previous part, make sure you use the unrounded value

An old car battery that has an emf of e m f1 = 11.5 V and an internal resistance of 55.0 mΩ is connected to an R = 2.00 Ω resistor. In an attempt to recharge the battery, you connect a second battery that has an emf of e m f2 = 12.6 V and an internal resistance of 10.0 mΩ in parallel with the first battery and the resistor with a pair of jumper cables.

(a) Draw a diagram of the circuit.

(b) Find the current in each branch of the circuit. (Enter your answers from smallest to largest.)

(c) Find the power supplied by the second battery. Assume that the emfs and internal resistances of both batteries remain constant.

Discuss where that power is delivered. Assume that the emfs and internal resistances of both batteries remain constant.

During 0.24 s, a wheel rotates through an angle of 2.42 rad as a point on the periphery of the wheel moves with a constant speed of 2.48 m/s. What is the radius of the wheel?

A box of mass m=19.0 kg is pulled up a ramp that is inclined at an angle θ=15.0∘ angle with respect to the horizontal. The coefficient of kinetic friction between the box and the ramp is μk=0.295 , and the rope pulling the box is parallel to the ramp. If the box accelerates up the ramp at a rate of a=3.09 m/s2, calculate the tension FT in the rope. Use g=9.81 m/s2 for the acceleration due to gravity.