Two cars collide at an intersection. Car A, with a mass of 1900 kg , is going from west to east, while car B , of mass 1400 kg , is going from north to south at 17 m/s . As a result of this collision, the two cars become enmeshed and move as one afterwards. In your role as an expert witness, you inspect the scene and determine that, after the collision, the enmeshed cars moved at an angle of 60 ∘ south of east from the point of impact. How fast were the enmeshed cars moving just after the collision? How fast was car A going just before the collision?

1. Why is there an electric field in a wire carrying a current if the wire is a conductor?

2. Which is easier and why, inserting a dielectric into a charged capacitor that is either connected or not connected to a battery?

3. Describe the motion of electrons moving through a conductor.

A hydraulic lift has two connected pistons with cross-sectional areas 20 cm² and 460 cm². It is filled with oil of density 590 kg/m³.

With the lift in balance with equal fluid levels, a person of mass 70 kg gets into the car. What is the equilibrium height difference in the fluid levels in the pistons?

How much did the height of the car drop when the person got in the car? h =

A curve of radius 68m is banked for a design speed of 80km/h .

f the coefficient of static friction is 0.36 (wet pavement), at what range of speeds can a car safely make the curve? [Hint: Consider the direction of the friction force when the car goes too slow or too fast.]

Express your answers using two significant figures separated by a comma. And express to Vmin, Vmax with km/h.

1. Using the Balmer formula calculate the first four wavelengths of the spectrum corresponding to n=3,4,5, and 6. Show your work.

2. Describe the possible orbits of an electron in a hydrogen atom that are allowed by the Bohr thoery.

3. What is the stationary state of the atom in Bohr theory?

(a) At what speed (in m/s) will a proton move in a circular path of the same radius as an electron that travels at 8.00 ✕ 106 m/s perpendicular to the Earth's magnetic field at an altitude where the field strength is 1.15 ✕ 10−5 T? m/s (b) What would the radius (in m) of the path be if the proton had the same speed as the electron? m (c) What would the radius (in m) be if the proton had the same kinetic energy as the electron? m (d) What would the radius (in m) be if the proton had the same momentum as the electron? m

Thermal energy ~ kT , where T is the absolute temperature (Kelvin) and k is Boltzmann's constant is an important benchmark... it is the energy available to electrons from their surroundings by virtue of random thermal motion.

The value of kT at room temperature is 0.026 eV or 26 meV.

What is the size, L, of the 3-D "box" in nanometers (a cube of side L) such that the energy difference between the ground state (1,1,1) and the first excited state (1,1,2) is about kT at room temperature?

A Honda Civic travels in a straight line along a road. Its distance x from a stop sign is given as a function of time t by the equation x(t)=αt²−βt³, where α = 1.48 m/s² and β = 0.0465 m/s³

^A)Calculate the average velocity of the car for the time interval t=0 to t= 2.02 s.

Express your answer in meters per second.

B)Calculate the average velocity of the car for the time interval t=0 to t= 4.03 s.

Express your answer in meters per second.

C)Calculate the average velocity of the car for the time interval t= 2.02 s to t= 4.03 s.

Express your answer in meters per second.

A 2.3 kg solid sphere (radius = 0.10 m ) is released from rest at the top of a ramp and allowed to roll without slipping. The ramp is 0.70 m high and 5.7 m long.

A.) When the sphere reaches the bottom of the ramp, what is its total kinetic energy?

B.) When the sphere reaches the bottom of the ramp, what is its rotational kinetic energy?

C.) When the sphere reaches the bottom of the ramp, what is its translational kinetic energy?

The starter motor of a car engine draws a current of 180A from the battery. The copper wire to the motor is 5.40mm in diameter and 1.2 m long. The starter motor runs for 0.960s until the car engine starts. How much charge passes through the starter motor? How far does an electron travel along the wire while the starter motor is on?

The drawing shows a positive point charge +q₁, a second point charge q₂ that may be positive or negative, and a spot labeled P, all on the same straight line. The distance d between the two charges is the same as the distance between q₁ and the spot P. With q₂ present, the magnitude of the net electric field at P is twice what it is when q₁ is present alone. Given that q₁= +3.87

This question recently appeared on Slashdot:

Slashdot posts a fair number of physics stories. Many of us, myself included, don't have the background to understand them. So I'd like to ask the Slashdot math/physics community to construct a curriculum that gets me, an average college grad with two semesters of chemistry, one of calculus, and maybe 2-3 applied statistics courses, all the way to understanding the mathematics of general relativity. What would I need to learn, in what order, and what texts should I use? Before I get killed here, I know this isn't a weekend project, but it seems like it could be fun to do in my spare time for the next ... decade.

It seems like something that would be a good addition to this site: I think it's specific enough to be answerable but still generally useful. The textbook aspect is covered pretty well by Book recommendations, but beyond that: What college-level subjects in physics and math are prerequisites to studying general relativity in mathematical detail?

In class, we learned that the electric field produced by a large, thin sheet of metal with a uniform distribution of charge is E=k2(pi)(Q/A)R^    where an area A has total charge Q and R^ point away from the sheet.  Two very large, very thin sheets of metal are parallel to each other as shown below end-on. Both sheets are charged; sheet A has +1 nC for each 1m^2 of area and sheet B has -2nC for each 1m^2 of area Determine the electric field in the three regions I, II, III that is produced by all the charge.

Area I is on the left side of sheet A. Area II is in between sheet A and B. Area III is on the right side of sheet B.

Find the binding energy per nucleon in J and eV for the three following isotopes, given their atomic masses in u:
¹⁹₅B   boron   19.06373 u

a) ______________×10^-12J ____________MeV


³³₁₄Si   silicon   32.97800017 u
b) ______________×10^-12J ____________MeV


²²₆C   carbon   22.0572097 u
c) ______________×10^-12J ____________MeV

^mproton=1.007276466 u
^mneutron=1.008664915 u
u=1.6605×10−27 kg

The diagram below is a top-down view of two children pulling a 10.7-kg sled along the snow. The first child exerts a force of F₁ = 16 N at an angle θ₁ = 45° counterclockwise from the positive x direction. The second child exerts a force of F₂ = 6 N at an angle θ₂ = 30° clockwise from the positive x direction.

(a) Find the magnitude and direction of the friction force acting on the sled if it moves with constant velocity.

(b) What is the coefficient of kinetic friction between the sled and the ground?

‪(c) What is the magnitude of the acceleration of the sled if F₁ is doubled and F₂ is halved in magnitude?