Conceptual Definition and 844 Threads

Homework Equations 1. You can always add two numbers that have the same units. HOwever, you cannot always add two numbers that have the same dimensions. Explain why not, and include an example in your explanation. 2. Can two nonzero perpendicular vectors be added together so their sum is zero...

Let's say Box A is 4 kg. It is accelerating and pushing against Box B, which is 20kg, is the force of A on B equal to the force of B on A? My gut instinct tells me the answer should be yes, but I don't understand why the boxes haven't stopped since the action-reaction forces cancel each other...

Any help will be appreciated:) 1) When a soda bottle is opened,gas bubbles rise up. Will they continue to rise if the bottle slips and starts falling? (Note:-I've noo idea what they mean!) 2) An hourglass is kept on a weighing machine. Will the weight recorded be more if all the sand is in...

Homework Statement http://img364.imageshack.us/my.php?image=90198228dt0.jpg Image: http://img364.imageshack.us/my.php?image=90198228dt0.jpg Which of the following statements are correct/incorrect? 1) The velocity is zero at point 4. 2) At point 6 the velocity is negative. 3) At point 3 the...

I'm a biochemistry major entering my junior year. After completing the requisite general physics course, I found that I quite enjoyed it and I wanted to take more advanced physics classes. I've set aside my junior year to take math classes necessary to be competent when I take my university's...

Homework Statement A stream of water flows vertically downward at a speed of v1 = 2.0 m/s from a faucet of cross sectional area A = 0.5 cm^2 to the bottom of a sink a distance h = 20 cm below. Homework Equations Bernoulli's P(atm) + (rho)gh = P(atm) + 0.5(rho)v^2 The Attempt at a...

Homework Statement n/a Homework Equations n/a The Attempt at a Solution n/a In my physics class we are learning about the EM radiation/wave nature of light/wave optics / image formation by mirrors and lenses, and I had a general question that was not really discussed in the...

Homework Statement Question 1: For each of the following objects answer three questions: Does it move with constant speed? Does it move in the same direction at every instant in time? Is its motion a consequence of Newton's first law? (explain your reasoning) a. the golden ball on the end of...

Hello -- I'm an upcoming junior in high school, and I'm trying to study some physics by myself in preparation for the physics class I will be taking. However, I am confused on the following conceptual questions about kinematics: 1). Traffic lights are often timed so that if you travel at a...

Thanks in advance for your help (and sorry about the lack of Latex...I didn't know how to type matrices in that format!) The textbook question itself is quite straightforward: Verify that A^2 - A - 6I = 0, given that A is a 2x2 matrix. (I is the identity matrix) It then goes on to...

I have a conceptual question regarding the self-induced emf in a solenoid coil. I have attached a graphic from Serway's Physics for Scientists and Engineers (6th edition) from Chapter 32 (Inductance). My question is regarding induced emf's (called "Lenz's law emf" in figures (b) and (c)) in...

Homework Statement A U-tube is filled with water, and the two arms are capped. The tube is cylindrical, and the right arm has twice the radius of the left arm. The caps have negligible mass, are watertight, and can freely slide up and down the tube. A one-inch depth of sand is poured onto the...

Homework Statement A rectangular wooden block of weight W floats with exactly one-half of its volume below the waterline. Masses are stacked on top of the block until the top of the block is level with the waterline. This requires 20g of mass. What is the mass of the wooden block? Homework...

Hi, This is probably quite a silly question, someone asked it to me but I have to admit I didn't know what to answer lol... The question is: A rotating ball has a rotational kinetic energy of K_{rot} = 1/2 I \omega^2, right? If you throw this ball (while rotating) up into the air, will it...

Hi guys I have some questions about electrostatics, and I hope you can help me. Here they are: 1) Please take a look at the following example...

Homework Statement Find an expression for the acceleration of m1. Homework Equations The Attempt at a Solution I did this earlier, and looking back on it I have a question: Sum of forces for m1: Fx= F2 on 1= m1a1 Sum of forces for m2: Fy = F1 on 2 + T1 - m2g = m2a2 I...

Hi all, I'm a little confused in answering these quantum physics based questions, as in order to give an answer I must support it with physics concepts. Here are they are: 1. What experiment confirms that light is radiated and absorbed in discrete amounts? Explain briefly how the experiment...

b]1. Homework Statement [/b] In the figure, is pressure at A larger than, smaller than, or equal to the pressure at B? [ Homework Equations The Attempt at a Solution My first instinct is that they are equal because they are at equal heights, but then again, isn't the pressure at...

1. The problem statement Suppose we have a thermodynamical system whose state is modified by external forces. This results in a change of the internal energy of the system. If we designate by W_{ext} the total work done during the process by the external forces acting on the particles of the...

Homework Statement If the inductance and the capacitance both double in an LRC series circuit, the resonant frequency of the circuit will... decrease to 1/4 its original value decrease to 1/2 its original value decrease to 1/8 its original value Homework Equations The Attempt at a...

Homework Statement A circular loop of wire is rotated at constant angular speed around an axis whose direction can be varied. In a region where a uniform magnetic field points straight down, what must be the orientation of the loop's axis of rotation if the induced emf is to be zero...

let's say a wheel rotates with a constant angular acceleration. Would its angular speed be affected if the radius was changed? It seems that angular speed would be independent of the radius since the angle is just a proportional quantity.

Hey guys I'm a year 12 student studying physics, and at the moment we are studying hydraulics. We learned that pressure varies with depth, which led me to this question. If I have two plates almost infinitely close together, each with a cross sectional area of A, would the total force on each...

A constant nonzero net torque is exerted on an object. Which of the following can not be constant? Choose all that apply. -angular position -angular velocity -angular acceleration -location of center of mass -moment of inertia -kinetic energy My guess is...

Hi all, If I have the wave function of a system, then the expectation of position is easily visualized as the centroid of the distribution. Does anyone know how to visualize the expectation of velocity given just the postion-space wavefunction (real and imaginary parts)

So, in the lab that my class just finished for angular momentum, we had a rotaring hollow cylinder rotating and we had to drop an iron disk square on top of it to measure the momentum before and after to verify conservation. The professor inquired how the result would be affected if we had...

I'm kind of confused as to how to determine when a vector field is conservative. For example, if we consider the following scalar field: \varphi = arctan(\frac{y}{x}) We see that the gradient is: F = \nabla\varphi = \frac{-y i + x j}{x^{2} + y^{2}} However, F is not a conservative...

Homework Statement There are four wires viewed end-on in the drawing. They are long, straight, and perpendicular to the plane of the paper. Their cross sections lie at the corners of a square. Currents of the same magnitude are in each of these wires. Choose the direction of the current...

Homework Statement I am having some trouble coming up with an answer to a couple of conceptual problems. 1. A car salesman claims that a souped-up 300hp engine is a necessary option in a compact car, in place of the conventional 130hp engine. Suppose you intend to drive the car within...

Homework Statement The circuit shown below consists of four different resistors and a battery. You don't know the strength of the battery or the value any of the four resistances. Select the expressions that will be equal to the voltage of the battery in the circuit, where V_{A}, for...

1) I was thinking about the definitions of KE and PE... can't the values KE and PE only ever be positive...? so ME = KE + PE Can total mechanical energy ever be negative? I'm thinking it cannot 2) also let's say you're in a car and you collide with another car... I'm trying to compare...

Homework Statement Block A is on top of Block B, which is on a frictionless incline. The mass of Block A is less than that of Block B. The positive x-direction is defined to be up the ramp. During the interval from t1 to t2 a hand exerts a constant force on block A in the positive...

Consider a wire, with current flowing through it. A small light insulator is brought close to the wire. The insulator has positive charge on its right end and a negative charge on its left end. But there is no net charge, it is neutral. What happens? Does the electrons in the current attract...

You have a cylinder with an ideal gas inside, enclosed by a piston. There is a valve on the side of the cylinder could let gas through if opened. The valve is then opened and some of the gas escapes slowly while maintaining thermal equilibrium. Once it is closed, the piston is a little lower...

Homework Statement If the sum(a_n) and the sum(b_n) are both divergent, is the sum(a_n + b_n) necessarily divergent? The Attempt at a Solution At first I thought it must be divergent, but then I asked, what if a_n is 1/n and b_n is -1/n... then their sum would be 0. Does this logic...

Homework Statement If a person stands on a level ground and throws a baseball, we say that a "launch angle" of 45 degrees will make the baseball travel farthest before it lands (ignoring air resistance). That is, the baseball has a maximum range when thrown at a 45 degree angle. But suppose...

Is it physically possible to syphon a liquid from a pool of water back to itself? My thoughts: Variables involved are acceleration due to gravity, change in height, surface tension, air pressure, friction, radius inside and vacuums. If you take all the air out of the tube and place both ends...

In a finite square well, there exists a non-zero component outside the well for all bound eigenstates. What is the physical nature of this non-zero component? How can you actually observe an electron outside the well when it is in a bound energy eigenstate? It would have an imaginary wave number.

Hello! We know that current flows in a circuit due to an electric field set up from the terminals which resembles that of a dipole, right? Now because it resembles the dipole's field, the electric field is NOT constant everywhere along the wire, and therefore, the electrons experience a...

I'm working on some homework and I've become stummped on two questions (one of them is wrong, the other is right). The bolded answer is the answer I've chosen. Homework Statement Question 3 10 points Save Which one of the following quantities is a vector quantity...

Hi all I took a course subject in basic statistics but its been so long ago I find that I have mixed up or forgotten some of the concepts so I hope someone here can help me refresh my memory. 1) Probability starts from 0 to 1, you can have any range of numbers but they cannot exceed 1 or...

Homework Statement Hi all. I have two questions (and two attempts) which I hope you can answer. 1) When I have a linear transformation L : V -> W, and I am asked to find the range (image) of this transformation, what is it exactly I am required to do? (I am not given the matrix A that...

[SOLVED] Conceptual question about torque and balls Homework Statement Take a look at the following thread: https://www.physicsforums.com/showthread.php?t=147053 In this thread, the torque is measured from the center of the ball. Can I measure it from the point where the ball and the...

Hiya, I'm really curious to know the rules of combining trig functions, say if: y = sin(x) + cos(2x) _How would I determine the period of the sinusoid (if it IS one) Is there a mthod of predicting if two sinusoids will compose another sinusoid, if there is I'm missing it. My textbook...

Homework Statement Two springs are connected, one is a heavy spring and the other is a light spring. A pulse is traveling down spring A, towards a junction with spring B. Which of the following statements are correct/incorrect. A. If spring A is the heavy spring then the transmitted pulse...

Homework Statement A 1 kg object is moving along at speed of 5 m/s right before colliding with a 4 kg stationary object, in a perfectly inelastic collision. Suppose that the objects are moving on a surface that has a coefficient of friction of mu=0.2. (Note you may still assume that the...

Hello, new poster here. I have trouble understanding some friction/resistance properties and how they are applied to rolling & linear motion simultaneously. I've done a lot of simple static / dynamic (sliding) friction examples as well as rolling without taking into account resistance, but...

Homework Statement Two blocks, A and B, are connected by a compressed string. The mass of bock A is twice that of block B. Immediately after release, compare the net force on block A to the net force on block B. The table is frictionless and the mass of the spring is zero. 1)There is no...

1. How do various distances influence the angular velocity of earth? Tangential velocity? explain Homework Equations 3. For some reason, I tend to think that distance doesn't relate, but I do not know where to begin to explain. I also could not find the answer in my physics book.

Homework Statement During a crash test, dummy x12 has a mass of 80 kg and rides in a 1120-kg car. Dummy y17 has a mass of 80 kg and rides in a 7120-kg truck. The vehicles approach each other with velocities of 30 m/s (about 67 miles per hour) in opposite directions (car heading east). The...