Laws Definition and 1000 Threads

I think it's a pretty simple question. Let's say we're talking about a moving elevator in which a person stands on a digital balance. The textbook tells me to treat the downward direction as positive, so the value of acceleration is 9.8 m/s^2 instead of -9.8m/s^2 I'm asked to find out the...

Hi. So if you have \frac{d p_{\alpha}}{ds} = \frac{q}{c} F^{\alpha \beta} u_{\beta} how could you possibly go on proving this its form is invariant under all coordinate transformations? Or any physical law of any form, really? I guess my point is how do you represent "all possible...

Homework Statement what is the coefficient of friction between a 41N bookcase and the groud, when the bookcase accelerates at .25m/s2? Homework Equations F=ma Forcefriction=μ*force normal The Attempt at a Solution a=.25 m=41 μ=? I have absolutly no idea what i am doing

Is Lorentz factor reality true according to the laws of physics?? Hi According to the laws of physics, the speed of light is independent of the speed of its source. In the example whereby there are two observers; one in the train moving at high velocity u relative to the other observer on...

Homework Statement If F = 8.0 N and M = 1.0 kg, what is the tension in the connecting string? The pulley and all surfaces are frictionless. Homework Equations F=ma The Attempt at a Solution 8-T=2a (2kg block) T - 1cos10? = 1a (for the 1kg block. I got stuck here, the angle threw...

Homework Statement The Attempt at a Solution I found the acceleration using kinematics equations. I don't know how to find the coefficient of friction though. I need help answering pard b c and d If you could give me the equations and explain. Just knowing how to do this one...

Homework Statement It includes a diagram so i just took a screenshot of the question. I don't undertand how to do this problem Thanks

A 1000kg boat is traveling at 90 km/h when its engine is shut off. The magnitude of the frictional force fk between boat and water is proportional to the speed V of the boat: fk = 70V where V is in meters per second and fk is in Newtons. Find the time required for the boat to slow to 45 km/h...

Homework Statement John (mass 80) rests on top of a light cube (mass = 0). A light rope passes horizontally from him over the front edge, and vertically down to Brian (mass 60kg) who hangs in contact with the front face as shown. The cube is on a horizontal surface and there is no friction...

Homework Statement At what rate is electrical energy converted to internal energy in the 4.56Ω and the 5.91Ω resistors in the figure? Homework Equations Kirchoff's Laws: ƩI(in) = ƩI(out) Junction Rule ƩΔV = 0 Loop Rule The Attempt at a Solution I have set the top branch current...

1. Homework Statement If a 25kg mass has a constant velocity of 5m/s, when pushed horizontally by a 5 N force, what amount of resistance force is present? 2. Homework Equations F=ma 3. The Attempt at a Solution I'm pretty sure the velocity is irrelevant, ... I made a...

Homework Statement A student decides to move a box of books into her dormitory room by pulling on a rope attached to the box. She pulls with a force of 130.0 N at an angle of 15.0° above the horizontal. The box has a mass of 25.0 kg, and the coefficient of kinetic friction between box and...

two containers are connected by a cord (of negligible mass) passing over a frictionless pulley (also of negligible mass). At time t = 0, container 1 has mass 1.30 kg and container 2 has mass 2.8 kg, but container 1 is losing mass (through a leak) at the constant rate of 0.200 kg/s. a) At what...

How does a spacecraft move in space where there is vacuum and nothing to provide normal reaction for the motion?

A 40 kg girl and an 8.4 kg sled are on the frictionless ice of a frozen lake, 15 m apart but connected by a roped of negligible mass. The girl exerts a horizontal 5.2N force on the rope. What are the acceleration magnitudes of (a) the sled (b) the girl (c) how far from the girl's initial...

How can you figure out the coefficient of static friction. I'm having a hard time understanding it.

An elevator cab and its load have a combined mass of 1600 kg. Find the tension in the supporting cable when the cab, originally moving downward at 12 m/s, is brought to rest with constant acceleration in a distance of 42m. Taking downwards as positive My solution: F net = mg - T = ma T =...

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...

Let’ say; “A” can see and measure a stone falls to the Earth let’s say 10 meter per 1 Earth-second. “B” lives at Mercury and can see the same thing. But “B” would do not see the exactly the same, because seen from “B’s” viewpoint time / distance is not the same as for “A”. Let us say...

Homework Statement Two weights are hanging by the following cables, A, B, C. 1. Find the tension in Cable A. 2. Find the tension in Cables B and C. -----ceiling---------- \ 60) (60 / \ / \ / B \ / C \ / \ / [_]...

Net force and Newton's laws of motion! Homework Statement A barge is hauled along a straight-line section of canal by two horses harnessed to tow ropes and walking along the tow paths on either side of the canal. Each horse pulls with a force of 490 N at an angle of 19° with the centerline...

Hello guys. I have a test in a couple of days, so I am hoping to get some practice. I'll post any questions I have here, I would appreciate if you guys can help me clear up any confusions. 1. A 400-N block is dragged along a horizontal surface by an applied force F as shown. The coefficient of...

Homework Statement A rocket that weighed 98.1 N when put together on Earth is attached to a 1.00 x 10^3-kg signal relay in intergalactic space. The rocket develops a constant thrust (i.e., it pushes with a force) of 10.0 kN. Compute the resulting acceleration. Homework Equations a=F/m...

Homework Statement they keep telling me it is a simple problem, I've actually done harder problems of the same thing, but i just don't seem to get this one. A 15kg block sits on a 25kg block. The coefficient of static friction between the blocks is 0.408 and there is no friction between...

Homework Statement The circuit in the figure is composed of two batteries (ε1 = 8 V and ε2 = 5 V) and four resistors (R1 = 110 Ω, R2 = 40 Ω, R3 = 50 Ω, and R4 = 50 Ω) as shown. Image: See Attachment OR: https://smart.physics.illinois.edu/images/phys102/Homework/03/cir06.gif Homework...

Is attraction always viewed as some kind of exchange of particles?

How are the various physical laws enforced in the universe? Even if there was only physical law out of which other laws manifest, how is that one physical law enforced?

thanks in advance for any and all help! The question is to show that Kepler's 3rd Law holds when you assume circular orbit with TWO gravitating bodies both orbiting around the center of mass. (by equating gravitational and centripetal forces and finding the constant of proportionality which...

I am 14 and know Newton's laws, but are there more basic laws of physics either then Newton's? If you could tell me or give me a link that would be great!

Homework Statement [PLAIN]http://img687.imageshack.us/img687/5055/imagelrl.jpg Homework Equations Static friction = (9.81sin60 x 0.2)N Centripetal force = mr(w)² The Attempt at a Solution I am only abl to get part (i), need hints for part (ii) and (iii). Thanks in advanced

The second law of thermodynamics states that the entropy in a system, such as our universe, always increases. The third law, however, says that entropy reaches zero as a system approaches absolute zero temperature. Our universe has been cooling off since its origin (because of its...

I would like to compile a short list of inverse-exponent force magnitude fall-off laws for several simple geometries for material made of monopoles and for material made of parallel dipoles (of negligible length). Far field force for any two objects is, of course, proportional to 1/r^2 for...

I came across this question, " An 8000 kg engine pulls a train of 5 wagons, each of 2000 kg along a horizontal track. If the engine exerts a force of 40000 N and the track offers a frictions of 5000 N, then calculate the force exerted by wagon 1 on wagon 2." In this question,if we consider...

Hello! I'm assuming the model of the Big Bang Theory and I'm asking specifically about the 'moment' of creation; I'm in no way well-versed in this; so please be gentle : * Are the laws of physics applicable to the beginning on the universe? * The Law of Conservation will not apply for this...

Why do I see Newtons 3 laws (mostly 2 and 3) given using differentials (F=dp/dt etc...) when it is far simpler to use the basic form F=ma (and the same for the 3rd law), is there an advantage to the more complicated form?

Homework Statement 2^-4 + 2^-6 _____________ 2^-3 Homework Equations The Attempt at a Solution Ive tried several times, I do the reciprical of all numbers ie) 1/2^4 + 1/2 ^6 ___________________ 2^3 Which gives me The wrong answer, cause i do the addiition first...

Homework Statement fill in the blanks. when a bird of weight W sits on a stretched wire, The tension in the wire is__________ Homework Equations Force(external)=mass*aceeleration The Attempt at a Solution tension should approach to infinity...

Homework Statement A pedagogical machine is illustrated in the sketch, yatta yatta, what force F must be applied to M_1 to keep M_3 from rising or falling? No friction. Here's the http://www.slideshare.net/brigittperalta/sol-maquina-pedagogica-1546585" . The Attempt at a Solution If we...

Homework Statement There are 2 blocks, one of mass m kept over other of mass 2m. Pls. refer to the diagram. The question is : the minimum value of u (coefficient of friction) between the 2 blocks for no slipping is : (a) F/mg (b) F/3mg (c) 2F/3mg (d) 4F/3mg My answer is coming as (b) but...

It seems to me that there is a difference between, say, the law of conservation of linear momentum or energy and the law of conservation of angular momentum. The first two are valid in any frame of reference and their invariance is a direct consequence of the relativity principle, whereas...

Please help me with this problem. many thanks :) A 55-kg bungee jumper has fallen far enough that her bungee cord is beginning to stretch and resist her downward motion. Find the force (magnitude and direction) exerted on her by the bungee cord at an instant when her downward acceleration has a...

Hello :) This is my question: A 325-kg boat is sailing 15 degrees north of east at a speed of 2 m/s. Thirty seconds later, it is sailing 35 degrees north of east at a speed of 4 m/s. During this time, three forces act on the boat: a 31 N force directed 15 degrees north of east (due to an...

1. A fully loaded Saturn V rocket has a mass of 2.92 x 10^6 kg. Its engines have a thrust of 3.34 x 10^7 N. a. What is the downward force of gravity on the rocket at blast-off? b. What is the unbalanced force on the rocket at blast-off? c. What is the acceleration of the rocket as it...

Hey, I have a test tommorow and I don't really understand gravitational potential energy or kepler's laws. It's not really a theory test, it's the math aspect, but I still don't understand it. I know of the formulas such as Fg=Gm1m2/r^2, Eg=Gm1m2/r, Ek=1/2 mv^2, and I think that's all. But...

A Particle is attached by a string to a point in a rough inclined plane of elevation \theta. Co-efficient of friction is \mu. Originally, the string is unstretched and lay along the line of greatest slope.Prove that the condition for particle to oscillate is \mu < 1/3tan\theta. Note : Tension...

Homework Statement 2^3 / 2^0 -2^-1 Homework Equations solving using exponent laws The Attempt at a Solution i move the negetive one over and make it 2^3 /2^0 = 1/2^1 I get 8 on the left side, and 2 on the right, bring the 6 from the right to the left and get 2. The answer is...

Hey, I have a question I'm stuck on for my grade 12 physics class. There is a block being pulled by tension over a triangle essentially that's at a degree of 35.7 (right angle triangle). I understand the whole question but I don't understand how to find how much pull the block has backwards of...

Kirchhoff's Three Laws of Spectroscopy are as follows. 1. An incandescent solid, liquid, or gas under high pressure, emits a continuous spectrum. 2. A hot gas under low pressure emits a "bright-line" or emission-line spectrum. 3. A continuous spectrum source viewed through a cool, low-density...

A 325-kg boat is sailing 15.0° north of east at a speed of 2.00 m/s. Thirty seconds later, it is sailing 35.0° north of east at a speed of 4.00 m/s. During this time, three forces act on the boat: a 31.0N force directed 15.0° north of east, a 23.0N force directed 15.0° south of west and F Find...

Homework Statement Two ropes are attached to a log that is floating in the water. A force of 80.0 N is applied to one rope and a force of 60.0 N is applied to the other rope, which is lying at an angle of 40° from the first rope. What is the net force on the log? We know that the angle...