Coefficient of friction, momentum, speed and distance

I have some physics questions: 1. It takes a force of 300 N to keep a 500-N box sliding across a floor. What is the coefficient of the sliding friction? 2. A force acting on a 5.0-kg body increases its speed uniformly from 2.0m/s to 8.0m/s in 3 s. What is the initial momentum of the body? What is the final momentum of th ...continues

Size Matters: Introduction to Nanoscience and Nanotechnology

Question: Calculate the proportion of atoms on the surface atomic layer of Ag spheres with the diameters below given that the thickness of the surface atomic shell is 0.289nm, stating any assumptions made. a) 1 micro meter b) 10 nm c) 5 nm

Calculating surface area

Silver density is 10,490 kg/m^3 and used to form spheres of different diameters. Calculate the surface area in m^2 of 1 g of Ag spheres.

Bonhoefer-van der Pol Equation

How do I describe the stationary points of the system of equations (attached) in the range -2< z <2? (c=3, a=0.7, b=0.8)

Scalar Potential

Please see the attached file for the adequate depiction of the scalar problem. A conservative force F can be written as F = -[upside down triangle]*phi symbol, where the phi symbol is called a scalar potential. Calculate the scalar potential for the gravitational force F = -k*abs. r/r^(2)

Explaining Global Warming

How would you explain global warming to a group of elementary students? Thanks.

Filtration Systems for Drinking Water

Do you think we should be working on filtration systems to make unsafe water drinkable? Why or why not?

Scarcity of Potable Water

In the world there is a scarcity of potable water. How might we solve this problem in the future? if you have any idea i am happy to learn from you and if you have internet site or books let me know with it i can learn more about the subject. Thanks.

Testing Understanding by Explaining to Elementary School Children

It has been said that you do not really know something until you can explain it to elementary school students using familiar words. What do you think? I would like some ideas on this matter.

The Uses of Spectroscopy

Question: What do scientists use spectroscopy for? Research the uses of spectroscopy and describe a use, and what we have learned from this use. Hi, I need some assistance with the above question. If you have some ideas, I would like to learn from you. Or, if you could give me some internet websites or book names I could lear ...continues

Activity for simulating the periodic table

Imagine that you want to create an activity for a group of children to simulate the periodic table. Suggest items that you may use and how they may be organized in rows and columns. If you have some ideas I'd like to learn from you and also if you know books or internet sites let me know so I can read and understand more. ...continues

What electromagnetic waves are dangerous for humans and why?

Sounds and Loudness

How loud is too loud? When is a sound too loud? What can be done about sounds/noises that are too loud for you? If you have some ideas I am very happy to learn from you.

What makes a ship float?

How is it that ships made largely of steel can float when the density of steel is much higher than the density of water? Why is it possible to make oil tankers much larger than other ships (and what happens when an oil tanker is unloaded?)

Pressure Variations and Ocean Exploration

How do the pressure variations with depth affect the ability to explore the ocean? How does it affect scuba diving and submarines? If you explain it to me and also if you give me internet site or reference book I would learn more. Thanks for your help.

Taking Advantage of Alternative Energy Sources

Why is it that our society has not taken advantage of alternative energy sources?

Hydraulic Cylinders

Explain how power is created using hydraulics and how a little cylinder on the tractor can raise or lower extreme amounts of implement weight. Explain the system including parts and functions.

Deciding Between Evolution and Creationism

Since science does not prove anything, neither the theories of evolution nor creationism are proven. Discoveries often presented as evidence are in fact just observations that did not disprove the theories or the hypotheses formulated based on the theories. How do I decide between these two theories? If you include references wi ...continues

Scientific Investigation

How do we do scientific investigation? I just want examples. Thanks for your help.

Theories widely accepted in the scientific community

Would you show me an example of a theory that is widely accepted in the scientific community? Thanks for your help.

The proof of science

Why do we say that science does not prove anything? I do not understand this; the science I know proves everything. If you have any ideas I'd be very happy.

Angular velocity and time

A person with a 50cm ponytail is using a lathe which is turning at 300rpm. The person turns their head, catching the end of the ponytail in the work piece, which has a diameter of 7cm. How long will it take the person's head to be dragged into the lathe?

Determining speed and direction of an aircraft

A. The pilot of an aircraft wishes to fly due west in a 50 km/h wind blowing towards the south. The speed of the aircraft, relative to the air is 100 km/h. In what direction should the aircraft head? (Answer in units of degrees from due East, with counterclockwise positive, within the limits of -180 degrees to +180 degrees). ...continues

Give 5 interesting facts about special relativity. Each one need only be 1 to just a few sentences - please list separately and provide any links to websites. These facts need not be anything original.

Discuss how the cosmic microwave background (a) is like an ether, (b) how it is not like an ether, and (c) why its existence has no effect on the Einstein postulates.

Energy Use

In the year 2011, the United States used about 115EJ of energy. 1. How many large power plants need to operate to meet that need? A large power plant provides about 1000MW. 2. If each square mile of a wind farm provides 3MW, how many square miles of wind farms would the US need? 3. How does this compare (use ratios) to ...continues

Static Equilibrium Question

A 646 N window washer is standing on a scaffold supported by a vertical rope at each end. The scaffold weighs 390 N and is 4.76 m long. Assume the window washer stands 1.03 m from the left end. What is the tension in the rope on the right? Answer in units of N

Given the equations of special relativity, show that there can be no more than one speed which is the same in all coordinate systems.

Given the equations of special relativity, show that there can be no more than one speed which is the same in all coordinate systems.

Magnitude field

A hydrogen atom in its ground state is subjected to an external magnetic field of 1.0 T. What is the energy difference between the spin-up and spin-down states?

Electron in the 3d state

An electron is in the 3d state of a hydrogen atom. Prove that the most probable distance of the electron from the proton is 9a_o.