Lost Definition and 564 Threads

Humans lost body hair in order to lose heat more efficiently according to this article. http://www.independent.co.uk/news/science/why-humans-lost-their-body-hair-to-stop-their-brains-from-overheating-as-we-evolved-8498623.html So , some humans moved out of Africa and into the cold regions of...

Hey all, is there a formula that can calculate the energy losy by a photon traveling through air at 1 atm per meter given frequency? Any help apreciated.

Let's say a spaceship from Earth (via a wormhole or something) suddenly found itself in a random place in the Milky Way galaxy. Assuming the crew possesses all of our current knowledge of the galaxy, and time was not a factor, would they be able to locate where our Sun is, and travel back to it?

It's my first time here, so I'm not sure if this is the right place to post it. If I post it in the wrong section, then I'm sorry. Anyways, I just have a curious question. Based on this video I watched --> "" at around 1:40:42 , I really want to know how she actually calculated the amount of...

So I am taking the second semester of intro physics and Moles,Molecular mass, Number of Molecules is killing me. I am not really able to solve my homework because I can never get these quantities down. I asked my professor for help during offie hours, however he said he teaches physics not...

Homework Statement A rope is used to lower a 1.1 kg bucket into a well at an acceleration of 1.9 m/s2. Determine the tension in the rope (in Newtons). Assume that air resistance is negligible and the acceleration due to gravity is -9.8 m/s2. Take the positive direction to be upward. Homework...

How is a continuous chain reaction maintained within a moderator if it is not fissile material? Are the fissile materials mixed with the moderator or are they coalesced at the center of the surrounding moderator? If it is the latter, how would the surrounding moderator allow fissile material to...

Hi simple question here, I was wondering if matter (actual particles) are lost from the fusion process.

This is really more of a qualitative question than a quantitative one. There is a history of some very depressing stories told on these forums (which certainly many people find through Google) of Ph.D holders without that desired tenure-track job, maybe working part time in a field entirely...

If electricity passes through a system at 12 volts, with 0.42 Amps of current, and 28.8 ohms of resistance, how do you calculate the energy lost in joules?

and all this time I thought it was just forgetfulness and senility setting in This explains so much :wink: ... cheers Dave

Homework Statement Two springs are joined and connected to a mass m such that they are all in a straight line. The two springs are connected first and then the mass last so that all three are in a row. If the springs have a stiffness of k1 and then k2, find the frequency of oscillation of...

I finished my bachelors a 2-3 years back in mathematics and working a pretty good job in New York in the tech industry, but I am having trouble deciding what to do next! My options are either continue down this route and become a product manager, go more heavily into software engineering...

Hello! I have been trying to make a simulation and it doesn't quite work right, don't exactly know why. I have two questions! 1. Acceleration I have been trying I need a formula that uses. frames till full speed (f) (if framerate is 60fps and this value is 60 then player is at full speed...

If a ball is dropped on a table it doesn't bounce back at the same height. Is this because some energy is lost to heat? If so, is this an example of friction, or is friction only when objects are being rubbed together?

Homework Statement A bullet of mass 2.0 * 10-3 kg is fired horizontally into a free-standing block of wood of mass 4.98 * 10-1 kg, which it knocks forward with an initial speed of 1.2 m s-1. (a) Estimate the speed of the bullet. (b) How much kinetic energy is lost in the impact? (c) What...

Homework Statement I suppose my question is a broad one. I am writing a Physics Extended Essay for the IB program (approx. 4000 words). My research question is "How does the angle of an inclined plane impact the horizontal translational kinetic energy of a solid cylinder [after it impacts and...

EDIT: I accidentally put this thread into Engineering instead of Mechanical Engineering section, please move! Hello all, I am designing a system which will basically just stand in two different positions all the time by a compressed spring. The spring is pushing the system while the forces on...

Homework Statement A rock of mass 1.10kg and volume 283cm3 is irregular shape. A person throws the rock with a launch angle of 39.0° (above the horizontal) over flat level ground from a height of 0.668m above the ground. Ground level is at an elevation of 138m above sea level. The rock goes...

Homework Statement We're assigned to build a ramp that launches our ball as high as possible. For now we're not taking any friction into account. Max height: 120cm Image: http://i.imgur.com/4DmX0mZ.png Homework Equations v = g * t Ep = m x* g * h Ek = (1/2) * m * v^2 The Attempt at a...

Hello, I'm 21 years old and no where near completing college. I'm currently in an engineering science program at my community college. I was originally going to an average state school for computer science and I did terrible at it and failed, this could be attributed to transition to college but...

Homework Statement A long wire carrying a 6.0A current perpendicular to the xy-plane intersects the x-axis at x=−2.0cm. A second, parallel wire carrying a 3.5Acurrent intersects the x-axis atx=+2.0cm. At what point on the x-axis is the magnetic field zero if the two currents are in the same...

Homework Statement [/B] I have two capacitors: 1-Farad capacitor A, and 9-Farad capacitor B. In state (a), I charged A with 1 Coulomb of charges, as depicted in figure (a). In state (b), I paralleled A with B, by doing this I discharged A, as depicted in figure (b). I try to find the total...

An Object slides with a consistent velocity down an incline that has a 30 degree angle. I'm trying to find the kinetic friction and the ratio that the mechanical energy is lost on the way down. I think I have already calculated µ with F(friction)= µmgcos(θ)=mgsin(θ) out comes Tan(θ) = µ I...

I've got a propane heater out of my deck that I use on cold days to enjoy a fine stogie and a port. It loses a lot of heat straight up. I'd like to redirect that heat back to me. (But safety first, I know.) I've been thinking of a simple curved sheet of aluminum suspended above it, but I'm...

All: I'm hoping you can assist me with this problem. My cat darted out the door and has been missing for two weeks. I recently had a sighting and would like to narrow down the search perimeter in order to try to locate my cat. So...I thought perhaps physics gurus may be interested in helping...

Homework Statement A team of dogs drags a 114 kg sled 1.92 km over a horizontal surface at a constant speed. The coefficient of friction between the sled and the snow is 0.124. The acceleration of gravity is 9.8 m/s 2 . Find the work done by the dogs. Answer in units of kJ. Find the energy...

Homework Statement I'm supposed to find the potential energy at the start of a system for a vehicle given that the mass is 4000kg, the total distance traveled is 800m, and 3/4 of the total energy is lost to heat and friction by the end of the distance traveled (it's assumed that the vehicle...

During entanglement photons get into an indeterminate state. The outcome of the photon state, on measurement, would now be random. Does this mean that, some of the, information the striking photon was carrying prior to transferring its energy to two entangled photons irretrievably lost? Even...

hello again, I am a physics undergrad finishing my last year, will graduate by the end of may... I am SO LOST and have no clue what I'm going to do next, mainly because in my country (Lebanon) physicists are limited to working at schools as teachers... This is something that i wouldn't enjoy...

Hi, so I recently graduated with a B.S. in Mechanical Engineering this past Spring. Since January I've been looking for employment, but I've had 0 luck. I have a 3.945 GPA and graduated magna cum laude, involvement in honor societies Phi Kappa Phi, Pi Tau Sigma, but I don't think that really...

So friction as a nonconservative force, is path dependent when it comes to how much work is lost from a system right? What confuses me however is understanding what that means, in terms of energy. So the work done by friction includes the energy that was neeeded to stop an obect (like a braking...

A 3-Star General Explains 'Why We Lost' In Iraq, Afghanistan http://www.npr.org/2014/11/09/361746282/a-3-star-general-explains-why-we-lost-in-iraq-afghanistan Trained for regular conflicts, the military seems ill-prepared for counterinsurgency. Seems like the same situation in WWI when the...

Not good. http://www.weather.com/news/science/virgin-galactics-spaceshiptwo-reports-flight-anomaly-20141031

Homework Statement During fusion of hydrogen to helium, 4 billion kg of matter are converted to energy each second. What fraction of the Sun’s total mass is lost each year to this process? Homework Equations None. The Attempt at a Solution First: Convert how many seconds are there in a year 1...

Hello I am currently a grade 11 student taking a 11U Physics course and we are nearly done our Kinematics unit and are finishing up Projectile motion. When i asked my teacher to explain the concept behind Projectile motion, i understood what a projectile is and what causes it (the force of...

Hi All, I am currently in my final year of engineering in Canada, and I'm starting to feel lost about what I want to do in life after graduation... whether to go get a masters or go work in industry. In regards to work, I believe my last co-op employer liked me enough to give me a good shot at...

Hello everyone, this is my first post here, and I hope I'm not asking a too "silly" question. I've already looked here and on the internet, but couldn't find a real answer to it. :) Here's the "silly" question. I was wondering the following, since: - The universe is inflating - The most distant...

Homework Statement a 28kg block starts at rest and slides down the incline ramp which is at an angle of 20 degrees up from the horizontal. the coefficient of kinetic friction between the incline and the block is 0.22. The height of the ramp is 2.5m. How much energy was lost to friction as the...

I tested out of my maths, and was placed in Calculus II, and being 16 I don't have time to be a full-time student (nor the mental capacity) so I only am taking two more classes, Physics I for Physics Majors, and Sociology. Going into the school year I felt very confident in Physics and kind of...

Hello! I have used Stewart's Calculus for the last year of Calculus and we made it through Taylor and MacLaurin Series. Next year we will be continuing. Since I really enjoyed calculus and I'm thinking of studying math/physics/computer science in college, I was looking for a good textbook to...

Hello I respect all of you I'm a computer programmer from Egypt When I finished my high school, I wanted to join the faculty of science math department My father refused because he has a private hospital and wanted me to be a doctor So I joined the faculty of medicine that I hated more than...

Hi everyone, my physics final is coming in 3 days:cry: , and I really need to have an answer to this exercise , but I'm stuck ! I don't even understand the problem statement HELP ! A typical fastball is thrwon at approximately 90 mph and with a spin rate of 113 rpm (I don't understand what it...

Homework Statement A block of mass 2kg, moving at velocity 2.68 m/s, slides across a rough 3m surface with a coefficient of kinetic friction of .4. Calculate the energy lost to the 3m rough surface. M=2kg uK=.4 V=2.68 m/s D=3mHomework Equations 1/2mv^2 uK*Fn*DThe Attempt at a Solution I used...

So, I was in my Mechanics 1 course and I was learning about the basic elements of gravitation as it is relates to tides and flux through various elements. I was bored to tears, the professor just wrote on the board, the class copied robotically, and I felt like my passion for science was...

Homework Statement A 2.8-m-diameter merry-go-round with rotational inertia 140kg⋅m2 is spinning freely at 0.40rev/s . Four 25-kg children sit suddenly on the edge of the merry-go-round. a) Find the new angular speed. b) Determine the total energy lost to friction between the children...

Homework Statement The statement below arises from a marble and track lab, and I'm enthralled to figure out a generalized equation ( variables only ) for energy lost per meter of track. Track is 12 feet long, but can be curved for hills and loops. Using a small section of track and marble...

A 100-W lightbulb generates 95 W of heat, which is dissipated through a glass bulb that has a radius of 3.2cm and is 0.60mm thick. What is the difference in temperature between the inner and outer surfaces of the glass? i am completely lost and need help

The Vector A points 17° counterclockwise from the positive x axis. Vector B lues in the first cuadrant of the xy plane. The magnitudes of the cross product and the dot product are the same: i.e, |AXB|= |A(times)B| What Angle does B make with the positive x axis? 2. Is ti a scalar...

Homework Statement A 2.00-kg object traveling east at 20.0 m/s collides with a 3.00-kg object traveling west at 10.0 m/s. After the collision, the 2.00-kg object has a velocity 5.00 m/s to the west. How much kinetic energy was lost during the collision? (no image was given). Homework...