Explain how X-ray observations are used to determine the temperature, T (r), and den- sity, ρgas, of the hot gas in an elliptical galaxy. What quantities are observed directly and how are they used to ultimately determine T and ρgas?

Ilya and Anya each can run at a speed of 8.30mph and walk at a speed of 3.90mph . They set off together on a route of length 5.00miles . Anya walks half of the distance and runs the other half, while Ilya walks half of the time and runs the other half.

How long does it take Anya to cover the distance of 5.00miles ?

Express your answer numerically, in minutes.

Find Anya's average speed.

Express Anya's average speed save,Anya numerically, in miles per hour.

How long does it take Ilya to cover the distance?

Express the time tIlya taken by Ilya numerically, in minutes.

Now find Ilya's average speed.

Express Ilya's average speed save,Ilya numerically, in miles per hour.

A mass (m) with speed (v) experiences a perfectly elastic collision with an initially stationary mass (M). What is the ratio of the masses (m/M) if after the collision, m and M have the same speed (V) but opposite velocities?

A nonconducting sphere 1.6 m in diameter with its center on the x axis at x = 4 m carries a uniform volume charge of density ρ = 5.4 µC/m³. Surrounding the sphere is a spherical shell with a diameter of 3.2 m and a uniform surface charge density σ = -2 µC/m². Calculate the magnitude and direction of the electric field at the following locations.

(a) x = 4.7 m, y = 0
  N/C î +   N/C ĵ

(b) x = 4 m, y = 1.5 m
  N/C î +   N/C ĵ

(c) x = 2.0 m, y = 3.0 m
  N/C î +   N/C ĵ

(please be careful with b and c last post was wrong

A 2.90-kg box is sliding along a frictionless horizontal surface with a speed of 1.8 m/s when it encounters a spring.

(a) Determine the force constant of the spring, if the box compresses the spring 5.30 cm before coming to rest.

(b) Determine the initial speed the box would need in order to compress the spring by 1.50 cm.

Carla and Jenny are arguing about whether or not it is possible to escape the gravitational field of the Earth. Carla shows Jenny a system where mass m is r_E (not the Earth's radius) distant from Earth and r_P (not planet P's radius) distant from planet P, the mass being on the line connecting the Earth and planet P. Carla states that the mass m has escaped if F_{P on m} = −F_{E on m}. Jenny disagrees. Which one, if either, is correct, and why?

How much energy is required to change a 60 g ice cube from ice at -25

The speed of sound is finite. This means that it has a specific, distinct speed, that we can calculate. Explain an every day example of how we know that the speed of light is finite.

Blocks with masses of 3.0 kg, 4.0 kg, and 5.0 kg are lined up in a row on a frictionless table. All three are pushed forward by a 19N force applied to the 3.0 kg block.

a) How much force does the 4.0 kg block exert on the 5.0 kg block?

b)How much force does the 4.0 kg block exert on the 3.0 kg block?

please explain! thanks!

What is the theoretical minimum frequency a photon must have in order to create a photoelectron? Show work to support your answer.

One of the difficulties of the Bohr model was that it assumes the existence of stationary orbits. Why was this problematic from a classical physics point of view? How does the solution of the Schrödinger equation remedy this situation?

As the temperature of a metal rod varies, so does the resistance and the dimensions of the rod. If a copper rod has a resistance of 4.78 Ω at 20.0°C, determine the resistance of the rod (in Ω) at 120°C by accounting for the changes in both the resistivity and the dimensions of the rod. The coefficient of linear expansion for copper is 1.67 ✕ 10−5 (°C)−1 and the temperature coefficient of resistivity is 4.04 ✕ 10−3 (°C)−1.

Snell's Law and the Law of Reflection explain how light is redirected when it encounters a surface between two media. In the extreme, light may only reflect at a boundary, and go back into the medium it was in. More often, some of it reflects and some goes through. If the boundary is plane and flat, then these laws are easy to interpret. When the boundary is curved, they describe happens at every point on the surface. One of the classic types of glass is called "crown" glass, which has an index of refraction for visible light of 1.52 and is usually free of significant impurities. It was one of the first glasses discovered, and windows are made from it. Another glass is called "flint" glass, and it has lead oxide added, which makes it heavier, more "dispersive", and increases its index of refraction to 1.62. 1. A ray of light enters a flat surface of crown glass at a 25 degree angle to the surface. At what angles do the reflected and refracted rays leave the surface? 2. As in the first part, but for flint glass, what are the angles? 3. For the flint glass, the refracted ray goes through the glass to the other side. If the glass is a parallel slab, what happens when the ray reaches the opposite side from the inside? At what angle to the surface does it exit the glass back into air? 4. What is the smallest angle to the surface that light can have and still be transmitted from the inside to the outside in the case of flint glass? What angle is the light going at as it leaves in that case? Hint: The laws of reflection and refraction are usually stated in terms of the angles to the perpendicular or "normal" to the surface. These questions are rephrased in terms of the angles to the surface so take care in interpreting the laws and your answers.

1. You have a massless, ideal spring with an unknown spring constant ?. You hang the spring from the ceiling. You then attach a mass (? = 21.0 kg) to the spring, which causes it to fall a distance of 2.75 m before stopping immediately before hitting the floor.

   (a) What is ??
   (b) Graph gravitational potential energy versus the position of the mass above the floor. (c) Graph elastic potential energy versus the position of the mass above the floor.
   (d) Graph the kinetic energy of the mass versus the position of the mass above the floor.