Homework Help

The goal of this board is to provide forum members an opportunity to learn how to solve physics problems. Use of this board should be targeted toward understanding how to solve a problem, learning as you collaborate with others, and preparing yourself for academic success. This board is not to be used to facilitate the mindless copying of homework or exam solutions. Consider your goals and how you use this board -- if you use it to learn, it's a great tool. If you use it to cheat, you're the one truly being cheated. Some general guidelines: Posters should show that they have attempted to answer the question prior to asking for help. Once your question has been respo…

How do you calculate magnitude of acceleration of a cart during the time interval t=0 second to t=0.30 second? (#7 on p 18 of workbook)

Found my answer.

Everyone in my household has tried working this problem and cannot come up with the given answer. A force F acts on a cart in motion on a frictionless surface to change its velocity. The initial velocity of the cart and final velocity of each cart are shown. You do not know how far or in which direction the cart traveled. Rank the energy required to change each cart's velocity from greatest to least. Cart A changes from 5 m/s to 2 m/s and has a mass of 2 kg. Cart B changes from 3 m/s to -3 m/s and has a mass of 3 kg. Cart C changes from 5 m/s to 6 m/s and has a mass of 5 kg. Cart D changes from -1 to 2 m/s and has a mass of 4 kg. Does this…

I don't understand the context of the 5th question of the Dynamics- Friction worksheet

The electric field just above the surface of the conductor charged plate in a machine has a magnitude of 3x10^5 N/C a) Derive an equation to find electric field on the surface of a big conductor plate. b) What is the surface charge density (in C/m^2) on the above mentioned plate, assuming that is a conductor?

Hi, I'm really stuck on this problem and I don't know how to solve it. I have a syringe full of water laid horizontally at a height of 4,9 meters from the ground. I want to calculate the distance that the water coming out of the syringe travels before hitting the ground (it acts like a projectile). A pressure of 100 Pa is applied to the "back" of the syringe (the thing of the syringe that when pushed expels water). The diameter of the back is 1 cm whereas the diameter of the little exit at the front is 2 mm. This is my strategy: I calculate the areas (by making sure to convert cm and mm to meters) and apply the continuity equation A1v1 = A2v2 so that I can fin…

I just watched this APlusPhysics video: https://www.youtube.com/watch?v=1wAwkyzxB0k I have a question for 2. a. Why is voltage across C0 equal to V0? I understand how this be the case if the resistor R1 was not there (since voltages are the same for components connected in parallel); however, since the resistor is connected to the capacitor in series, wouldn't the voltage V0 be split across C0 and R1 (which means C0 would have a voltage less than V0)? Also, for 2. b - I originally thought that I2 would increase, because when the switch is first closed, the capacitor acts like a wire and allows current to flow freely, so the current will be split between both th…

Hi, I'm confused about this question: "A proton is moving to the right at constant speed v and enters a region with uniform magnetic and electric fields. It continues to move in a straight line. The magnetic field is directed toward the top of the page. What is the direction of the electric field?" Using the right hand rule, with fingers pointed to the right and curled fingers up, my thumb points out of the page, leading me to believe that would be the answer. The correct answer is actually that the electric field points into the page. Why is this? Thank you!

Hello, This question features a circuit with a resistor, an inductor, and a battery all connected in series. It then shows an increasing concave down graph of something vs. t - the graph started at the origin and had a horizontal asymptote at some positive value of x. The "something" could be: A. The potential difference across the resistor B. The potential difference across the inductor and/or C. The current in the circuit. I had reasoned that it would be all 3. When an inductor is first connected to a battery at time t=0, it doesn't allow electricity to flow, but as time goes on, it allows more and more electricity to flow until it is essentiall…

A bricklayer lifts 1.2 kg bricks and places them on a 140 cm high wall. If the bricklayer puts in an 8 hour work day working at the rate of 0.050 hp, how many bricks does he lift?

Page 80, question #4.12 in the book... I'm not understanding the worked out solutions, especially why the tensions were subtracted. Explanations would be appreciated

I need help solving question 7 in the APlus Physics 1 essentials book in appendix A on kinematics. There isn't much of an explanation for the answer. Thanks!

At t = 0, a particle leaves the origin with a velocity of 18.7 m/s in the positive x direction and moves in the xy plane with a constant acceleration of (-1 i + 4 j) m/s2. At the instant the y coordinate of the particle is 18 m, what is the x coordinate of the particle?

Is the equation sheet given for the Multiple Choice on both the AP physics c exams? I know the past exams only gave table of information for the MCs. Does the current exam give equation sheet and table of information for the MCs?

So in the phase diagram, since the temeprature doesn't change while phase changing, does the internal energy also not change?

On gangnam style problem (AKA ap style), on number 7, I think the answer is C=D>A=B>E could you check on that.

I am attempting to solve a rolling without slipping problem but I am having a very difficult time getting the correct answer. A force is being applied to the object at an angle of 37o above the horizontal and I am trying to find the maximum value of |F| for the object to roll without slipping. There is static friction present on the ground. I think my mistake lies in setting up the net torque. Does the force F contribute to the net torque? I know that the friction force does. Will I cross r into F at 37o?

On ap style number 7 on magnetics, shouldn't the answer to b be cos instead of sin? Where did you get sin from?

In ap style problem section, #8 on fluid section, isn't the net force 800-4-707??? In the explanation you talked about the pressure holding the lid, but you didn't include in the net force.

On question 7.33, there isn't sufficient explanation for the answer. Could you elaborate on that please? I'm not sure what is causing the needle to point toward the top. By the way, does toward the top mean out of the page or just top?

Om 7.27, I don't understand the picture. I'm not sure how the wire can produce emf when the wire doesn't have an area of change. The answer says it's moving horizontally, but isn't the wire just moving without changing the area?

In the electricity part of the AP style problems, I think there is an error for #8. I think the initial current is 0.6 instead of .75. Shouldn't R2 and R4 be in series? Then, R24 (combined) would be 2R. R234 (combined) would be in paralled and be 2R/3. Then, the Req would be R1+R234 (R+2R/3) which is 5R/3. Then wouldn't the current be 3/5? Not .75.

For #2 of the Gravity part of the AP style problem, I'm not sure why speed has to increase in order to increase the radius. I thought speed has to decrease because of the inverse relationship with radius according to the derived equation, v = square root of Gm/r.

For #14 of the circular motion & rotation part of the AP style problems, for (c) why is the answer 2L/t instead of L/t? I don't understand why the L was doubled.