a 1.0 kg ball and a 2.0 kg ball are connected by a rigid massless rod. The rod and balls are rotating clockwise about their center of gravity at 20 rpm. What torque will bring the balls to a halt in 5 seconds?
The correct answer is -0.28 N.m. I can't figure out how to get this answer. Please do not answer this question with an incorrect answer as it will be a waste of both our times.
In: Physics
the position vector of a mass 2.0 kg is given as a function of time, t, as
r= (3.0 m) i + (4.0 m/s)t j.
What is the angular momentum of the particle about the z axis?
please explain and answer!
In: Physics
An object’s position is described by the equation x = At – Bt 4 + C. What are the dimensions of (a) A, (b) B, and (c) C? (d) Find the time derivative of position, dx/dt. (e) What are the dimensions of the time derivative?
In: Physics
A child on a sled is travelling a total distance of 93 m down a dirt hill with an angle of 30 degrees from the horizontal from the top of the hill. The mass of the child and sled is 65 kg. The initial velocity is zero and the final velocity is 5.0 m/s. (a) What is the time it takes to travel down the hill? (b) What is the acceleration down the hill? (c) What is the force of friction? (d) What is the coefficient of kinetic friction?
In: Physics
Two stationary positive point charges, charge 1 of magnitude 3.05nC and charge 2 of magnitude 1.75nC , are separated by a distance of 44.0cm . An electron is released from rest at the point midway between the two charges, and it moves along the line connecting the two charges.
What is the speed vfinal of the electron when it is 10.0cm from charge 1?
Express your answer in meters per second.
In: Physics
How will you align the compass and the large coil in earths magnetic field to get meaningful data? What measurements and calculations will you make?
In: Physics
Can you think of a way of performing soft lithography on curved surfaces like a glass optical fiber? Why would you want to do that?
Soft lithography is inherently a 2D printing technique, can you think of a way to taking to the third dimension? Why would this capability be useful?
In: Physics
A charge of 22.0 μC is held fixed at the origin.
(A)
If a -6.00 μC charge with a mass of 3.10 g is released from rest at the position (0.925 m, 1.17 m), what is its speed when it is halfway to the origin? v=__m/s
(B) Suppose the -6.00 μC charge is released from rest at the point x = 12(0.925m) and y = 12(1.17m). When it is halfway to the origin, is its speed greater than, less than, or equal to the speed found in part A? Explain
(C)Find the speed of the charge for the situation described in part B. v=__m/s
In: Physics
What is the energy of the photon that, when absorbed by a hydrogen atom, could cause the following?
(a) an electronic transition from the n = 3 state to the n = 6 state
(b) an electronic transition from the n = 3 state to the n = 8 state
In: Physics
What are ways in which businesses pose a threat to the environment? In dealing with environmental harm, what should be the guiding principle for businesses?
In: Physics
A 1.00Kg horseshoe at 900°C is put in a 4.00Kg bath of water at 10°C. assuming that no energy is lost by heat to the surroundings, determine the total entropy change of the wather + horesehoe system. (HINT think about dQ_r)
In: Physics
1 of 20
Which of the following is the most accurate statement concerning charge?
| a | Charge is one of the seven fundamental dimensions found in nature. |
| b | Charge is a derived dimension (current • time), with SI units of Coulombs. |
| c | Charge is a derived dimension (current • time), with SI units of amperes. |
| d | Charge is a fundamental quantity found in all elementary particles such as protons, electrons, and neutrons. |
| e | The electrical force between two charges is directly proportional to the distance between the two charges. |
Question
2 of 20
Which of the following is the most accurate statement concerning electrical force?
| a | Electrical force is a derived dimension, with SI units of Newton/meter. |
| b | In most cases, the electrical force between two particles is roughly equivalent to the gravitational force between the particles, but opposite in direction. |
| c | Electrical force is one of the seven fundamental dimensions, with SI units of Newton. |
| d | Electrical force obeys the inverse square law. |
| e | Like the gravitational force, the electrical force is always attractive, never repulsive. |
Question
3 of 20
Which of the following is the most accurate statement concerning the first law of thermodynamics?
| a | The first law of thermodynamics describes the relationship between systems in thermal equilibrium. |
| b | The first law of thermodynamics describes the relationship between heat, work, and internal energy in a thermodynamic system. |
| c | The first law of thermodynamics describes the conservation of energy in an open thermodynamic system. |
| d | The first law of thermodynamics describes the conservation of energy in a closed thermodynamic system. |
| e | More than one of given statements are accurate. |
Question
4 of 20
What is the most accurate statement concerning the second law of thermodynamics?
| a | The Carnot cycle involves an isothermal expansion followed by an isobaric compression. The efficiency of this partial cycle is normally about 96%. |
| b | The second law of thermodynamics requires heat to flow spontaneously from a cooler object to a warmer object. This is the basis for a refrigerator. |
| c | A closed thermodynamic system absorbs heat at a high temperature and then converts the heat absorbed into useful work at a lower temperature. |
| d | An isothermal process requires the temperature and pressure in a closed thermodynamic system to remain constant. |
| e | No cyclic thermodynamic process can convert heat completely into mechanical work. |
Question
5 of 20
What is the most accurate statement concerning the relationship between entropy and the second law of thermodynamics?
| a | Entropy provides a quantitative measure of the disorder of a system. |
| b | Entropy is equal to the ratio of the heat added to a system and the absolute temperature of the system. |
| c | Like energy, entropy is required to be conserved in both reversible and irreversible thermodynamic processes. |
| d | More than one of these statements (a, b or c) are accurate. |
| e | None of the statements (a, b or c) is accurate. |
Question
6 of 20
If you run a Carnot heat engine in reverse, which of the following statements must be true?
| a | Heat enters the gas at the cold reservoir and goes out of the gas at the hot reservoir. |
| b | The amount of heat transferred at the hot reservoir is equal to the amount of heat transferred at the cold reservoir. |
| c | The engine is able to perform a net amount of useful work, such as pumping water from a well, during each cycle. |
| d | The engine can transfer heat from a cold object to a hot object. |
| e | More than one of the above statements are true. |
Question
7 of 20
What is the most accurate statement concerning Gauss's law?
| a | Gauss's law provides a quantitative relationship between the electric field established and the quantity of charge present when two point charges form a dipole. |
| b | Gauss's law provides a quantitative relationship between the scalar nature of electric force and the vector nature of electric flux. |
| c | Gauss's law provides a quantitative relationship between electric charge and the electric field associated with the electric charges enclosed on the surface of a three-dimensional object like a sphere. |
| d | Gauss's law uses superposition to estimate the scalar difference between lines of electric flux entering or leaving a closed two-dimensional surface. |
| e | More than one of the statements (a, b, c or d) are accurate. |
Question
8 of 20
If the electric field is "E" at a distance "d" from a point charge, its magnitude will be 2E at a distance______
| a | d/4. |
| b | d/2. |
| c | d/?2. |
| d | d ? 2. |
| e | 2d. |
Question
9 of 20
Two protons close to each other are released from rest and are completely free to move. After being released, which statement(s) is/are accurate?
| a | Their speeds gradually decrease to zero as they move apart. |
| b | Their speeds gradually increase as they move apart. |
| c | Their accelerations gradually increase as they move apart. |
| d | Their accelerations gradually decrease to zero as they move apart. |
| e | More than one of the statements (a, b, c or d) are accurate. |
In: Physics
1) Suppose one force vector is 100 N at theta= 45 degrees, and a second force vector is 75 N at theta =123 degrees both with respect to the positive x-axis. What is a third force that would cause zero net force if all forces are acting on the same mass particle?
2) Suppose one force vector is 150 N at theta = 45 degrees, and
a second force vector is 172 N at theta =
300 degrees both with respect to the positive x-axis. What is a
third force that would cause zero net force if all forces are
acting on the same mass particle?
In: Physics
3) Consider a very (infinitesimally!) thin but massive rod, length L (total mass M), centered around the origin, sitting along the x-axis. (So the left end is at (-L/2, 0,0) and the right end is at (+L/2,0,0) Assume the mass density λ (which has units of kg/m) is not uniform, but instead varies linearly with distance from the origin, λ(x) = c|x|.
d. In the limit of large z what do you expect for the functional form for gravitational potential? (Hint: Don’t just say it goes to zero! It’s a rod of mass M, when you’re far away what does it look like? How does it go to zero?) What does “large z” mean here? Use the binomial (or Taylor) expansion to verify that your formula does indeed give exactly what you expect. (Hint: you cannot Taylor expand in something BIG, you have to Taylor expand in something small.)
e. Can you use Gauss’ law to figure out the gravitational potential at the point (0, 0, z)? (If so, do it and check your previous answers. If not, why not?)
In: Physics
Calculate the Coulomb barrier height (in terms of MeV) for two
nuclei, each with mass number 9 and atomic number 4, when they are
just touching.
In: Physics