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Questions tagged [homework-and-exercises]

Applies to questions of primarily educational value - not only questions that arise from actual homework assignments, but any question where it is preferable to guide the asker to the answer rather than giving it away outright. Please READ THE GUIDANCE IN META before asking homework-like questions.

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Calculating RPM of a motor

I am trying to calculate the optimal RPM of a DC motor in order to move a car. I know that the force exerted on the wheel by the motor is: $$F=9N$$ I also know the following information ("h" ...
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Why are there 6 interactions with 4 positive charges?

From a homework assignment, there are 4 spheres spaced 1cm apart. Each of the spheres are charged to +10nC and weigh 1 gram. The question wants us to find the final speed of the charges once they've ...
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If the cross-sectional area of a wire doubles shouldn't the current also double?

In this question the answer is B but I don't understand how that could be possible considering the area has doubled.
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How to calculate and express $*d*F$ in index notation?

Gravitation by Charles W. Misner, Kip Throne and John Wheeler page 120 Box 4.4 Duality Plus Exterior Differentiation, related exercise 3.13, 3.17 I want to calculate the component of $*d*F$ in index ...
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Physics Superposition

If the width of both slits is increased without changing their separation of a. State the effect of the brightness of the light fringes and dark fringe. The brightness of the light fringe will ...
16 views

The acceleration needed to stop a car in time [on hold]

Say you are driving at the speed of 30 m/s, when suddenly a car in front of you, which was previously traveling at the same speed, brakes. If you press your brakes 0.455 s later, what would the ...
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How to find the ideal intersection between constant object and controllable object?

So I'm an engineer who's a bit out of practice, but have taken up a side project for entertainment purposes. I'm trying to teach myself to code and find myself struggling to come up with a solution ...
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How do you determine whether answer is A or D? [on hold]

How do you tell the difference between graphs A/D from t=0 to their maximum postions given this eqaution.
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A bead on the wire loop

In my physics book there is a question which stated is as follows: A thin circular loop of radius $R$ rotates about its vertical diameter with an angular frequency $\omega$. Show that a small bead ...
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Who will win the race?

There is a wedge which is inclined at an angle X to the horizontal.Supppose two carts of same mass M one having 3 wheels and the other having 4 wheels are released from rest at the top of the incline,...
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Finding the maximum shear value acting on a beam [on hold]

Here is the setup if the beam: As I cut the beam at 4m from the left(fixed wall). It gave a shear force of zero. If I cut it 3m from the right I get a shesr force of 5kN. Well I am not totally sure ...
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Magnetism question from REE (Roorkee Entrance Examination) 1991 [on hold]

A short magnet of magnetic moment 6 A.m2 is lying in a horizontal plane with its North Pole pointing 60 degrees east of north.Find the net horizontal magnetic field at a point on the axis of the ...
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Frame of Reference in Kinematics

If we have two frames of reference, say S1 and S2, and the acceleration of a particle as seen from both the frames has equal magnitude, say 4 m/s^2, then shouldn't the frames have no relative ...
36 views

Line charge inside a conducting sphere? [on hold]

I could not find any example like below. How can we solve this question? I tried to solve like sum of the point charges along the z axes but I am not sure if I am wrong or right. I think the shape of ...
37 views

What is the best angle to throw a rock across a distance? [on hold]

If i were to throw a piece of rock, across a river of x metres wide, what would be the best angle of elevation i should throw the rock with, so that the rock can land x metres away with minimum force ...
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How do i calculate the speed of the ball? [on hold]

A spring pushes a 15 grams ball with 10 m/s in a bent pipe. What is the formula to calculate the speed of the ball in point A and point B. The pipe is horizontal so there is no g-force and the pipe ...
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In the circuit the switch was in position 1 for a long time and at t=0, it is thrown to position 3. Find current as function of time t after switching

I started solving the problem by finding the steady state current. Then as the switch was shifted to position 3 the current in the inductor would decay. But my teacher told me that the current ...
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Lagrangian mechanics a cylinder on a cylinder barrel

This is a typical problem to be solved using the Lagrangian mechanics, but I have a problem in understanding the rotational energy. The task is to formulate the Lagrangian equation for the system of ...
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Finding the average speed plus a break [on hold]

I have the following equation when the driver drove 2.5h at 120 km/h and then stopped for 30 minutes. Then he drove for 20 minutes at 25 m/s. The result of the equation is to determine the average ...
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Direction of acceleration vector at the apex of a curve

(Test Your Understanding of Section 3.2) The question wants me to choose the correct acceleration vector, from the given 9 options where 9th option is zero acceleration. Ok, first I thought option ...
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Electric potential of a charged spherical conductor using laplace equation

Reviewing a course of electromagnetism I encountered the problem of a spherical conductor with a charge of $Q$ in a uniform electric field. The problem of a conductor in a uniform electric field (a ...
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Do the oil and mercury in this manometer affect the pressure in A and B?

One of my friends came to me with this homework question: We've worked out that the height difference between A and B is 50 mm. That makes the difference in pressure between them  \Delta P = \rho ...