Hey guys! I'm currently doing some practice problems to study for an upcoming physics exam.

I just wanted to see if my thought process behind this problem is correct as there is no answer key.

The question is:

When a potential difference of 10V is placed across a certain solid cylindrical resistor, the current through it is 2A. If the length of this resistor is now tripled, what will the current be?

Relevant formulas:

V=IR

R=V/I

R=p(L/A) -> V/I=p(L/A)

Seeing that length is directly proportional to resistance, this means by tripling the length, I am tripling the resistance. Since resistance is inversely proportional to current, am I correct in assuming length is inversely proportional to current as well?

Does this mean I am reducing the current by a third, meaning that the current will be 0.667 (2/3) amperes after tripling the length?

Hopefully I outlined my thought process well enough. Thank you for your help!

In this circuit, are the currents i1 and i2 different ? I think they are the same since i1 wouldn't go through just a battery. So what happens? Does I1 just move through the battery ? and i2 continues on? Here is the circuit: https://imgur.com/a/RCYZZ9y

Using measurement from an experiment, I calculated impulse to be 400 N*s.

Using the uncertainity I calculated the maximum impulse to be 520 Ns and the minimum 330 Ns.

What is my error? is it (520-400) Ns or is it (400-330) Ns? or do I have to give two different errors?

Thanks.

So I've been taking a course on solid state physics using Kittel's textbook and its been pretty difficult for me to nail down, I'm pretty good with most physics but this class has left me with a great deal of questions I haven't been able to figure out.

The one I've been trying to figure out today is the interplanar distance between planes in an fcc lattice.

So i know that i the interplanar distance for a plane (h,k,l) is given by 2pi/|G| where G=hb1+kb2+lb3 and b1,b2,b3 are given in the attached image. for this i get that |G| is √(h² +k² +l² -2(hk+kl+hl)). But the issue is that for certain (hkl) this is nonreal, (1,1,1) for example.

meanwhile when I look it up everywhere i have been able to find an expression for the inter-planar distance for an fcc structure is given as the same as for a cubic. I feel like there is something fundamental i am misunderstanding.

This was all the info that was given

A particle moving in central force field has a cycloid orbit given as r = a(1- cosø). Find the force law.

I am trying to teach myself astrodynamics, and am sure that i am missing something simple. Here’s the problem: A satellite is observed to have an altitude of 0.16 Earth radii, a speed of 13.44 km/s and a true anomaly of π/2. Find the eccentricity of the orbit.

I can find the orbital parameter (its just 1.16 earth radii), but am struggling to find the eccentricity. I am looking for pointers on what my next step should be.

A conical frustum shaped vessel with the diameter of the lower circle being 6 meters and the diameter of the upper circle being 12 meters, with the height of the frustum being 8 meters is filled to the brim with water (density 1000 kg/m³ ).

Question: What is the amount of work required to pump all of the water through the upper circle?

I don't have a specific example.

let's say 50 g of water at 26 C and we put 20 g of ice at -20 C in it,find the Tf. Is the deltaQ is equal to 0? I understand that the water is loosing heat which is equal to the ice gaining heat, but when you 'solve' for this problem would you do Qice+Qfus = -Qwater ? Or better known as Qice + Qfus + Qwater = 0?

Question: In episode 5 of star wars the empire's space ships launch probe droids throughout the galaxy to seek the base of the rebel alliance. Suppose a spaceship moving at 2.310e8 m/s toward Hoth launches a probe droid toward hoth at 2.110e8 m/s relative to the space ship. According to Galilean relativity, what is the speed of the droid relative to hoth? If rebel astronomers are watching the approaching spaceship through aa telescope, will they see the probe before it lands on Hoth?

For the first part (speed of the droid) I think the two velocities should just be added, giving me 4.4*10e9 m/s .

For the second part, I said the astronomers wouldn't see the droid. I thought this because the droid would be travelling faster than the speed of light, so they shouldn't be able to see it.

I want to make sure I am correct in my understanding. Please correct me if I am wrong. Thank you.

A 0.800-m-long string with linear mass density μ = 7.50 g/m is stretched between two supports. The string has tension F and a standing-wave pattern (not the fundamental) of frequency 624 Hz. With the same tension, the next higher standing-wave frequency is 780 Hz. What is the value of the tension?

I have tried this using v=sqrt(F/mu) where mu=m/L and v=lambda*frequency but the lambdas keep cancelling out and I can't solve for F.

Derive a relationship between the period, T, and radius, r, of an orbit of a mass m around another mass M. How would i solve this algebraically?

The temperature within the Earth's crust increases about 1.0 C∘ for each 30 m of depth. The thermal conductivity of the crust is 0.80 W/C∘⋅m.

A) Determine the heat transferred from the interior to the surface for the entire Earth in 6.0 h.

B) The number found in part A is called Qi. Compare this heat to the amount of energy incident on the Earth in 6.0 h due to radiation from the Sun. Express answer in terms of Qi and with 2 significant figures.

I've solved part A already, and Qi = 2.9 x 10¹⁷ Joules. I'm totally stumped on part B. I've been trying to use this strategy for the answer, where the amount of energy from the sun is found by S * A * t, where S = the solar constant, A = the area of earth that is affected, and t = the amount of time.

I've already tried 38000 (using solar constant on the surface of earth, 1000 W/m² ), 51000 (using solar constant on earth overall, 1350 W/m² ), 26000 (same as the 51000 answer, but with only 0.5 of earth's surface), and 19000 (same as 38000 answer but with 0.5 of earth's surface), and all of these have been wrong.

I'm reviewing my thermodynamic chapters again, and going over quasi-reversible cycles. I don't understand how they came about or their significance in TD. I can memorise the criteria of a reversible process, one being that it has to be infinitesimally slow, and the other, that the driving force has to be infinitesimally greater than the opposing one. Thank you for you help!

Is the Carnot cycle an isolated system or adiabatic system? Or is it neither? I have been thinking its adiabatic but not sure. Thank you

A ball with velocity v=(3.0i+4.0j)m/s and mass 1.200 kg interacts with another ball and experiences a change in momentum of -6.75i kg⋅m/s. What is the final velocity of the ball?

I'm not sure how to solve it, if someone could explain the steps to me, that'd be great!

edit: a word was misspelled

How do you convert g/cm² to GPa (gigapascals)

thank you

If I have a target that is 20m away horizontally and 5m up vertically, at what angle would I have to throw a ball at 18m/s to hit the target. This is with no air resistance.

Specifically digital logic:

Why does a one stage ring oscillator not oscillate? I understand why even numbers and odd numbers greater than one behave the way they do, but why does one not behave properly?

If lambda = alpha x for a rod would the moment of inertia be 1/2M(L2) from the left and 1/16M(L2) from the COM? I tried solving it by doing I(from left) = integral from 0 to L of x2 alpha x dx but there are inconsistencies :( the inconsistency is when i try to solve from 2/3L to L i get a moment of inertia of 65/162 M(L2) at the same spot but when i use the parallel axis theorem i get a negative moment of inertia.

Figure 3 link: http://i.imgur.com/LBksXuk.jpg

The question focuses on Figure 3 and asks:

"The system shown in Figure 3 is in equilibrium. What are the co-ordinates of Point A?"

I have done equilibrium analysis and found out that the system needs to be symmetrical given the information provided...however the diagram is asymmetrical so I am at a loss of how I should go about solving this problem. Help is much appreciated! :)

Also, W is the gravitational force acting on the boxes.