Physics - October 2007

I have to find the coefficient of knietic friction between a shoe and a wooden board. I have managed to get the static friction by placing the shoe on the board and raising it until the shoe starts moving. The only materials I can use is the wooden board, shoes and a metre stick. I have tried one way, but my teacher says it isn't accurate enough, and I haven't been able to devise an experiment that would help me find the coefficient of kinetic friction. If anyone has some tips or ideas on how to do this, I would be very grateful for their help.

2007-10-14 13:43:09 · 1 answers · asked by smiley5671 2

What are the current theories as to why its all over the place? Not "because the more mass you've got the more gravity" but why does mass have gravity in the first place.

Also is it theoretically possible to make energy from gravity? It sound plausible since gravity is like a force... but im guessing the reason this isn't considered much is because it goes against the laws of thermodynamics, i think, right? Or is it a possibility??

2007-10-14 13:28:24 · 3 answers · asked by Anonymous

A horizontal force of 150 N is used to push a 36.0 kg packing crate a distance of 6.25 m on a rough horizontal surface. If the crate moves at constant speed, find each of the following.
(a) the work done by the 150 N force
I got 937.5 J
(b) the coefficient of kinetic friction between the crate and the surface
????HELP!!

2007-10-14 13:00:52 · 1 answers · asked by Anonymous

2007-10-14 12:55:14 · 2 answers · asked by Kelly 1

Gold has density of 19.3 103 kg/m3. What would the radius of a solid gold sphere have to be if the acceleration due to gravity at its surface is to be 9.81 m/s2? Check your answer against the radius of the Earth, which has a mean density of 5.5 103 kg/m3.
r = _____km???

2007-10-14 12:50:38 · 1 answers · asked by baron 2

what is the acceleration of a ball dropped? is it -9.81 or 9.81

2007-10-14 12:46:56 · 4 answers · asked by Desilicious 1

A 10 g, bullet is fired into a 10 kg wood block that is at rest on a wood table. The block, with the bullet embedded, slides 5 cm across the table. What was the speed of the bullet?

( coefficients of static and kinetic friction are not given but from a table in the book wood on wood coefficient are:
static= 0.5
kinetic= 0.2
I thought that might help!)

This is question 38, from chapter 9 of book:
Physics for Scientist and Engineers, By Knight

2007-10-14 12:40:31 · 2 answers · asked by Anonymous

A 71 kg climber is supported in the "chimney" by the friction forces exerted on his shoes and back. The static coefficients of friction between his shoes and the wall, and between his back and the wall, are 0.83 and 0.65, respectively. What is the minimum normal force he must exert? Assume the walls are vertical and that friction forces are both at a maximum.

2007-10-14 12:39:17 · 1 answers · asked by lcbby 1

2007-10-14 12:38:06 · 2 answers · asked by Anonymous

A 5.00 kg block is placed on top of a 12.0 kg block that rests on a frictionless table. The coefficient of static friction between the two blocks is 0.600. What is the maximum horizontal force that can be applied before the 5.00 kg block begins to slip relative to the 12.0 kg block, if the force is applied to (a) the more massive block and (b) the less massive block?

2007-10-14 12:34:21 · 2 answers · asked by tazk 1

Gold has a density of 19.3X10^3 kg/m^3. What would the radius of a solid gold sphere have to be if the acceleration due to gravity at its surface is to be 9.81 m/s^2? Check the answer against the radius of the Earth, which has a mean density of 5.5X10^3 kg/m^3. radius of a gold sphere =? Please help as I have put in my fair share of helping others on here...I am by no means a physics wiz.

2007-10-14 12:24:08 · 1 answers · asked by Anonymous

consider two cubes an aluminum cube, an iron cube that both have an edge length of 3.0 cm.

1. which cube if either has greater mass.
2.which cube displaces the more water when fully submerged?
3. which cube experiences the buoyant force of greatest magnitude when fully submerged?
4. calculate the magnitude of the buoyant force in newtons acting on the aluminum cube and the iron cube when each submerged in water.
5. if either block is immersed only half-way into the water, how does the magnitude of the buoyant force in this case compare to the buyoant forct when tat same block is fully submerged?

thank you very much for the help.

2007-10-14 12:23:46 · 1 answers · asked by u.p. 1

A machine in an ice factory is capable of exerting 2.83*10^2 N of force to pull a large block of ice up a slope. The block weighs 1.00*10^4 N. Assuming there is no friction, what is the maximum angle that the slope can make with the horizontal if the machine is to be able to complete the task?

2007-10-14 12:14:59 · 1 answers · asked by Anonymous

2007-10-14 11:46:09 · 1 answers · asked by Doc 2

Describe briefly the main benefits and shortcomings of communication satellite systems
including for example, their orbits, propagation delays, the nature of the radiation and the
antennae used, and energy requirements.

2007-10-14 11:15:43 · 1 answers · asked by sa7era 1

A box 21.6 kg box initially at rest is pushed 2.36 along a rough horizontal floor, with a constant applied horizontal force of 56.2958 N. The acceleration of gravity is (9.8m/s^2). If the coefficient of friction between the box and the floor is 0.188,

1.find the work done by the friction. answer in J.

2. Find the final speed of the box in units of m/s

2007-10-14 11:15:21 · 1 answers · asked by contraseña 1

2007-10-14 11:13:01 · 1 answers · asked by Anonymous

I'm finding the net magnetic field at a point 10.0 cm to the right of two wires that have currents going opposite directions.

2007-10-14 11:10:37 · 1 answers · asked by Anonymous

Hello.Here is a problem i can't solve, so i am asking your help!

Two points K and L of an elastic medium,which is doing a harmonic wave with a frequency f=90 Hz, have phases at the moment t1, phase(K)=15π/4 rad and phase(L)=3π/2 rad.How much time needs the wave to cover the distance of those 2 points???

2007-10-14 11:03:00 · 1 answers · asked by Anonymous

havent you heard of the "disclosure" project or "fastwalkers".
check them out, enlighten yourselves.

2007-10-14 09:09:33 · 3 answers · asked by Terrybear 1

A swimmer is capable of swimming 0.30 m/s in still water.
(a) If she aims her body directly across a 75 m-wide river whose current is 0.60 m/s, how far downstream (from a point opposite her starting point) will she land?
m
(b) How long will it take her to reach the other side?
s

2007-10-14 09:09:04 · 1 answers · asked by kdcheerldr 1

A diver running 1.6 m/s dives out horizontally from the edge of a vertical cliff and 2.9 s later reaches the water below.
How high was the cliff?
m
How far from its base did the diver hit the water?
m

2007-10-14 09:06:28 · 1 answers · asked by kdcheerldr 1

A hypothetical planet has a radius 1.7 times that of Earth, but has the same mass. What is the acceleration due to gravity near its surface?

What is the distance from the Earth's center to a point outside the Earth where the gravitational acceleration due to the Earth is 1/20 of its value at the Earth's surface?

Suppose the space shuttle is in orbit 410 km from the Earth's surface, and circles the Earth about once every 92.8 minutes. Find the centripetal acceleration of the space shuttle in its orbit. Express your answer in terms of g, the gravitational acceleration at the Earth's surface.

Thank you

2007-10-14 09:06:00 · 1 answers · asked by Suzumi A 2

A solid sphere of uniform density starts from rest and rolls without slipping a distance of d = 2.8 m down a q = 29° incline. The sphere has a mass M = 5.8 kg and a radius R = 0.28 m
a) Of the total kinetic energy of the sphere, what fraction is translational?
b) What is the translational kinetic energy of the sphere when it reaches the bottom of the incline?
c) What is the translational speed of the sphere as it reaches the bottom of the ramp?
d) Suppose now that there is no frictional force between the sphere and the incline. Now, what is the translational kinetic energy of the sphere at the bottom of the incline?

I don't know where to start. Please help. Thanks!! :)

2007-10-14 09:02:54 · 1 answers · asked by Anonymous

Hello! I have 3 questions:

A 15 kg uniform disk of radius R = 0.25 m has a string wrapped around it, and a m = 4.6 kg weight is hanging on the string. The system of the weight and disk is released from rest.
a) When the 4.6 kg weight is moving with a speed of 1.3 m/s, what is the kinetic energy of the entire system?
b) If the system started from rest, how far has the weight fallen?
c) What is the angular acceleration at this point?

I don't know how to start. Any help/ideas? Thanks :)

2007-10-14 09:00:18 · 1 answers · asked by Anonymous

2007-10-14 08:09:29 · 3 answers · asked by Rafael G 2

my teacher gave us this work sheet for homework over the weekend yet never taught us what is on it. My parents helped me with most of it but i wanted to try this second part on my own. i am doing ok but here are the 2 problems i cant solve..

What are the net forces of a car stopped at a light??

A horse exerts a force of 15N on the ground, What is the magnitude of the reaction force?What does the reaction force act on?

Please help me and tell me how you go the answer. I am baffled. haha.

2007-10-14 08:03:59 · 6 answers · asked by liveitup 2

Why do white things reflect light back, while black absorbs it? Don't just repeat my question if you know what I mean, I'm asking WHY.

2007-10-14 07:55:36 · 2 answers · asked by Big Boss the Philosopher 6

2007-10-14 07:28:56 · 6 answers · asked by Rafael G 2

radius of the curve is 20m

2007-10-14 07:03:29 · 1 answers · asked by Anonymous