Imagine SETI astronomers discover a world with intelligent life.  

Should we make contact? Please write a 2 paragraph response with the following structure:

Paragraph 1: Two reasons why we SHOULD make contact. Two reasons why we SHOULD NOT make contact.

Paragraph 2: Your conclusion including the basis for your judgement.

Let’s say you push the block from the bottom of the plane all the way up to the top of the plane, then let it slide back down.

11-1. While you are pushing the block up the plane, is the work done by gravity positive or negative? Why?

11-2. While you are pushing the block up the plane, is the work done by friction positive or negative? Why?

11-3. As the block slides back down the plane, is the work done by gravity positive or negative?

11-4. As the block slides back down the plane, is the work done by friction positive or negative?

11-5. What is the net work done by gravity over the entire cycle (being pushed all the way up and then sliding all the way back down)? Is it positive, negative, or zero?

11-6. What is the net work done by friction over the entire cycle (being pushed all the way up and then sliding all the way back down)? Is it positive, negative, or zero?

Discuss the physical significance of the equivalent magnetization current densities J_m and J_ms.

Can we utilize them as current sources to run a circuit? If YES/NO, why do you think so?

While exploring a castle, Exena the Exterminator is spotted by a dragon who chases her down a hallway. Exena runs into a room and attempts to swing the heavy door shut before the dragon gets her. The door is initially perpendicular to the wall, so it must be turned through 90∘ to close. The door has a height of 3.00 m and a width of 1.15 m , and its weight is 720 N . You can ignore the friction at the hinges.

If Exena applies a force of 250 N at the edge of the door and perpendicular to it, how much time does it take her to close the door?

Use 9.80 m/s2 for the acceleration due to gravity.

Strontium 38Sr90 has a half-life of 29.1 yr. It is chemically similar to calcium, enters the body through the food chain, and collects in the bones. Consequently, 38Sr90 is a particularly serious health hazard. How long (in years) will it take for 99.9488% of the 38Sr90 released in a nuclear reactor accident to disappear?

An object is 15.2 cm to the left of a lens with a focal length of 10.2 cm. A second lens of focal length 11.8 cm is 39.27 cm to the right of the first lens. The height of the object of is 2.1 cm. What is the location of the final image with respect to the second lens? What is the height of the image?

(a) Stations A and B are at the same sea surface elevation level and have a bottom depth of 2000 m. Both stations have seawater with a uniform density with respect to depth; however the seawater density at A and B are different (sA = 24.7 kg/m3 ; sB = 25.4 kg/m3 ). [A = 40o 45' N, 25o 45' W; B = 41o 5' N, 24o 45' W]

(b) Does this current vary with respect to depth ? If so, explain how it varies and why

A 25kg block is placed 2.7m above the ground on a frictionless ramp. At the bottom of a ramp there is an ideal spring.

A. If the block is let go, how fast will the block be moving at the bottom of the ramp?

B. The block runs into the spring and compresses the spring a total of .35m before coming to a stop. What is the spring constant of the spring?

The block then slides back up the ramp. How high (above the ground) does the block get before coming to a stop?

Why doesn't great mass automatically equal great inertia?

A bungee cord is 30.0 m long and, when stretched a distance x, it exerts a restoring force of magnitude kx. Your father-in-law (mass 93.0 kg ) stands on a platform 45.0 m above the ground, and one end of the cord is tied securely to his ankle and the other end to the platform. You have promised him that when he steps off the platform he will fall a maximum distance of only 41.0 m before the cord stops him. You had several bungee cords to select from, and you tested them by stretching them out, tying one end to a tree, and pulling on the other end with a force of 420 N .

When you do this, what distance will the bungee cord that you should select have stretched?

Two of the three electrons in a lithium atom have quantum numbers of n = 1, l = 0, ml = 0, ms = +1/2 and n = 1, l = 0, ml = 0, ms = -1/2. What quantum numbers can the third electron have if the atom is in (a) its ground state and (b) its first excited state?

A hydrogen atom is in the ground state. It absorbs energy and makes a transition to the n = 5 excited state. The atom returns to the ground state by emitting two photons, one in dropping to n = 4 state, and one in further dropping to the ground state. What are the photon wavelengths of (a) the first and (b) the second transitions?