Block Definition and 998 Threads

Please forgive another round on the block universe, but I had a brief visit with Paul Davies and wanted to give the folks on the forum a report along with some quotes from his book. Sorry for the lengthy post. I was at a high school reunion in Phoenix last weekend and was staying with my...

Homework Statement A 0.500-kg block is attached to a horizontal spring that is at its equilibrium length, and whose force constant is 23.0 N/m. The block rests on a frictionless surface. A 5.60×10^-2 kg wad of putty is thrown horizontally at the block, hitting it with a speed of 2.00 m/s...

Homework Statement A block of mass m=2.4kg is attached to a string that is wrapped around the circumference of a wheel of radius r=7.6cm. The wheel rotates freely about it's axis and the string wraps around it's circumfrence without slipping. Initially, the wheel rotates with an angular...

Homework Statement A block moves on the frictionless slide shown in the diagram. What is the minimum height from which the block can be released if it is to complete the loop without leaving the surface of the slide? (Assume that the dimensions of the block are small compared to R, and that...

I have a discussion about shielding of noise generated by appliance and florescent lights. I know both Al and Cu are not magnetic material. BUT all noise are time varying meaning it is EM field. Good conductor block E field as loss is very high. How does that work when only the B field can pass...

I have a question on block that I was solving in my book. I got the answer right but different procedures for doing it I want to make sure my logic is correct,and I didn't get the answer out of probability. Two crates of mass 75kg and 110kg, are in contact and at rest on a horizontal...

Hello, I've been stuck on this problem and would really appreciate if someone could help me: A block of mass MB = 4.75 kg is initially at rest on a level rough surface for which the coefficient of kinetic friction is given by uk = 0.455 . Two bullets of equal mass Mb = 0.023 kg are moving...

Homework Statement a .46kg block is attached to a horizontal spring that is at equilibrium length, and whose force constant is 22 N/m. The block rests on a frictionless surface. A 5.2x10-2 wad of putty is thrown horizontally at the block, hitting it with a speed of 2 m/s and sticking. How...

Homework Statement a .440 kg block of wood hangs from he ceiling by a string, and a 7.3x10^-2 kg wad of putty is thrown straight upward, striking the bottom of the block with a speed of 5.50 m/s. The wad of putty sticks to the block. is the mechanical energy of this system conserved? how...

Homework Statement Hi guys. First of all, great forum you've got here. I have a problem and I hope you can help me with this one. Block of mass m lies on a rough horizontal surface. In the period 0 - t1, the block is moving due to the force F(t), which varies depending on the time. In...

A bullet of mass m = 19.7 g traveling horizontally at speed vo = 445 m/s strikes a block of mass M = 854 g sitting on a frictionless, horizontal table. The bullet comes out the other side of the block at speed v = 415 m/s. What is the speed of the block after the bullet exits the block? Using...

Homework Statement A small wooden block with mass 0.750 kg is suspended from the lower end of a light cord that is 1.48m long. The block is initially at rest. A bullet with mass 0.0118kg is fired at the block with a horizontal velocity V0. The bullet strikes the block and becomes embedded...

Homework Statement A small block with mass 0.0400 is moving in the xy-plane. The net force on the block is described by the potential- energy function (5.80 )-(3.50 ). Homework Equations inverse tangent of Fy/Fx = angle of acceleration The Attempt at a Solution The question...

Homework Statement Consider the track shown in the figure. The section AB is one quadrant of a circle of radius 2.0 and is frictionless. B to C is a horizontal span 3.5 long with a coefficient of kinetic friction = 0.27. The section CD under the spring is frictionless. A block of mass 1.0...

Homework Statement A mass m = 13kg is pulled along a horizontal floor with no friction for a distance of d = 5.1m. Then the mass is pulled up an incline that makes an angle theta = 39 degrees with the horizontal and has a coefficient of kinetic friction u = 0.39. The entire time the...

I’m relatively new to Physics Forums, so please go easy on me guys. I’m trying to get an understanding of the so-called Block Universe concept and its implications, but I need help. I’m going to start out by articulating my current understanding, and then try to apply this understanding to...

A block slides a distance d down a frictionless plane and then comes to a stop after sliding a distance s across a rough horizontal plane, as shown in the accompanying figure. What fraction of the distance s does the block slide before its speed is reduced to one-third of the maximum speed it...

Homework Statement A box slides across a frictionless floor with an initial speed v = 3.2 m/s. It encounters a rough region where the coefficient of friction is µk = 0.1. If instead the strip is only 1.56734693877551 m long, with what speed does the box leave the strip? Homework Equations...

When I galvanize iron or attract a more reactive block of metal to iron, that metal will oxidise instead of the iron. I understand that anions need to be present for the reaction to occur as the more reactive metal will have transferred its electrons to iron. So the eg magnesium will oxidise to...

A spring (75 N/m) has an equilibrium length of 1.00 m. The spring is compressed to a length of 0.50 m and a mass of 2.2 kg is placed at its free end on a frictionless slope which makes an angle of 41 degrees with respect to the horizontal. The spring is then released. a) If the mass is...

Homework Statement coefficient of kinetic friction = 0.15 Find the acceleration of block a. Homework Equations see below The Attempt at a Solution http://www.wolframalpha.com/input/?i=-200sin30%2B0.15*200cos30%2B2x%3D-200%2F32.2*a%3Bx-40%3D40%2F32.2*b%3Ba%3D0.5*b I used x for...

I'm having trouble solving for two variables in Mathcad. I'm relatively inexperienced with this software and I'm not sure whether it's the software or my math but anyway I've included screen dumps to highlight the problem. I have tried the Given/Find block in two different ways. The first does...

Homework Statement 1. Homework Statement A block of mass 0.015kg enters the bottom of a circular, vertical track with a radius R = 0.3m at an initial velocity of 4/ms. If the block loses contact with the track at an angle of 130 degrees, what is Wk, the work done by kinetic friction...

Homework Statement A block of mass 15g enters the bottom of a circular, vertical track with a radius R = 0.5m at an initial velocity of 4/ms. If the block loses contact with the track at an angle of  = 130, what is Wk, the work done by kinetic friction...

Homework Statement A 80-kg block is pulled across a rough surface a distance of 1.25 metres. How much work was done in moving it? The coefficient of static friction was 0.3 and kinetic friction was 0.2. Assume the velocities were very low. Homework Equations W = fd ?? The Attempt at...

Homework Statement A car and pulley system are setup as shown. Find the acceleration of the car. The car wheels have a friction coefficient of 0.15. The car has a mass of 0.05 kg while the block has a mass of 0.02 kg. http://sadpanda.us/images/836771-GBD7SB9.jpg *sorry if the picture is bad I...

1. See the following picture: http://imageshack.us/photo/my-images/715/math5610.jpg/ Essentially what I'm trying to do is solve a linear block system. I have got to the point where I now need to "add multiples of the top rows to clear out C." Now, I'm sure this is the easy part as I've...

Homework Statement An experiment consists of pulling a heavy wooden block across a level surface with a spring force meter. The constant force for each try is recorded, as is the acceleration of the block. The data are shown below: Force F in Newtons: 3.05 | 3.45 | 4.05 | 4.45 | 5.05...

A mass m is moving at a speed of Vo and slides smoothly onto a sloped big block of mass M. The big block can also move on the table surface. Assume that everything moves without friction. After the small block reaches the height h on the slope It slides down. Find the height h. Problem Number...

In the drawing is described a system to the control flow of a liquid. The control is done by changing the rotary speed of the electrical engine that moves the pump. Changing of the speed is done by changing the voltage for the motor.BUILD A BLOCK...

I am having trouble trying to obtain Y/R from the block diagram below: the only thing i understand so far is that the bottom right loop is a feedback loop and can be simplified to 1/(s+a1). i know b1s can be obtained from the right loop, but i am having trouble getting to that point. i know it...

Homework Statement A cubical block of wood, 10 cm on a side, is placed in a glass cup whose higher end is open to the atmosphere. The wood is in equilibrium at the interface between water and oil with wood’s lower surface 2 cm below the interface. The density of oil is 790 kg/m3. a) What is the...

Hi,guys,What is evidence against and for block universe theory?

A block of mass m remains at rest on an incline. The force acting up the ramp on this block is a. 0 b. mg c. less than mg d. more than mg I understand that the force of friction cannot be more than the force of gravity because it would then move upward... but how is that the force of...

More threats to the open research community. Between this and SOPA... http://www.nytimes.com/2012/01/11/opinion/research-bought-then-paid-for.html?_r=1&scp=1&sq=research%20works&st=cse

Homework Statement A block of mass 4.2 kg which has an initial velocity of 3.3 m/s at time t=0, slides on a horizontal surface. If a constant friction force of 10.2N is exerted on the block by the surface, what is the acceleration? Homework Equations Work Energy Theorum? .5 m vo2 -...

Hi friendz I have a problem. If a block of mass m is placed over the wedge such that there is no friction then what is the acceleration of block 1with respect to wedge 2 with respect to ground Pleas reply. Thanks in advance. My sir said that it is different.Is it so.

Dear friends I have a problem in creating a block tridiagonal matrix. I try to create a block tridiagonal matrix in MATLAB and I tried everything but it is not working for me. I have matrices A, B, C of dimension 4*4. Elements od these matrices are dependent on (n) and in each n has different...

Homework Statement A block of mass m is held motionless on a frictionless plane of mass M and angle of inclination θ. The plane rests on a frictionless horizontal surface. The block is released. What is the horizontal acceleration of the plane? (Introduction to Classical Mechanics by David...

A block of mass m is positioned at the top of a quarter-circle ramp with radius R and friction coefficient μ. To find the velocity v at the bottom, I did the force summation equations in the n- and t-directions and came up with: n: N - mgsinθ = mv^2/R t: mgcosθ - μN = ma I then solve for...

Dear forum members How to block tunneling current? Apart from barrier dimensions like height and thickness are there any other options? Say barrier geometry or chemical property, maybe some magnetic impurity to induce Kondo effect and scatter the tunneled electrons. Thank you in advance Dilema

Homework Statement Given the following block diagram. Calculate the transfer function H(z) and find \theta (f=\frac{f_{s}}{6}) Homework Equations H(z)=\frac{Y(z)}{X(z)} The Attempt at a Solution Ok So I know i need to find my y(k) output equation from this. I can then rearange the...

Homework Statement A block of mass m is moving at a speed of v0 at a distance L away from a spring of on a table with coefficient of friction μk. How much does the block compress the spring? Determine the average power generated due to friction during the compression of the spring. I'm not...

1. So this is a very basic question on tension, i assume, however every example provided in my book shows the tension within two cords. I can't seem to grasp the correct way to do this... Homework Statement A 2 kg block is suspended from a single rope. A horizontal force keeps the cord at...

Homework Statement A(n) 9 g bullet is fired into a 396 g block that is initially at rest at the edge of a frictionless table of height 0.9 m. The bullet remains in the block, and after impact the block lands 2.3 m from the bottom of the table. The acceleration of gravity is 9.8 m/s. Homework...

Homework Statement A 2.0 kg block is released from rest on a frictionless 30 degree incline. After sliding 0.80 m it comes in contact with the spring, and after sliding an additional 0.20 m, it comes momentarily to rest. What is the spring constant? I knew that spring constant is equal to...

Homework Statement A(n) 9 g bullet is fired into a 303 g block that is initially at rest at the edge of a frictionless table of height 1.9 m. The bullet remains in the block, and after impact the block lands 1.5 m from the bottom of the table. The acceleration of gravity is 9.8 m/s/s. Find...

Homework Statement block of mass m = 5 kg is connected to a spring having stiffness constant k = 49 N/m, as shown in the figure below. The surface between the block and the table has μk = 0.1 In this figure, the block is presently held in place with the spring stretched by x1 = 0.8 m...

Homework Statement A 50 g bullet at 50 m/s hits a block 2.0 m away. The coefficient of friction is 0.30. What is the force of bullet on the block, the velocity of the block and bullet and distance traveled by the block? Assume this is a perfectly inelastic collision. Known: m_b = .0050kg...