# Tagged Questions

Questions related to mathematical physics which include application of mathematics to problems in physics and the development of mathematical methods suitable for such applications and for the formulation of physical theories

26 views

### How to make vector from azimuth and speed?

I don't know how to make $3$D vector of speed from azimuth and speed. Azimuth is in degree and speed is in m/s. Azimuth is angle on $X$ and $Y$. Thank you for your help!
41 views

### Least squares regression with two predictor variables (exponential functions of time)

Question cropped from textbook (Apologies for the link- I don't have enough rep to post the actual image.) [Now pasted below. Ed.] I've come across a question in a textbook (linked above) requiring ...
455 views

35 views

### Find an function that oscillates between a given upper and lower envelope

Suppose I'm given two real, continuous functions $f(x)$ and $g(x)$ such that $f(x)\ge g(x)$ for all real $x$. I'd like to determine an oscillating function $h(x)$ that has $f(x)$ as its upper-envelope ...
13 views

### Simulation missiles - initialization vector

I'm trying to implement a simple simulation of the trajectory of bullets. Only for school project. I am using formula: ...
21 views

### How to calculate work done on standing a rod upright with arbitrary mass distribution m(x)

I was way overthinking how to calculate calories that you would do performing a pullup, which is a straightforward mgh. But with a sittup, you have some non-uniform torso that's being lifted to ...
53 views

### Hydrostatic force on a dam

A dam is inclined at an angle of 30° from the vertical and has the shape of an isosceles trapezoid 200 ft wide at the top and 100 ft wide at the bottom and with a slant height of 160 ft. Find the ...
40 views

### Rocket simulation. Are my equations correct?

I am simulating a rocket launch (two dimensions) and I am a little unsure about my implementation of Euler Forward. I will only give the $x$ component since $y$ is done the same way. I first ...
68 views

### Having trouble simultaneous trigonometric equations

I'm racking my brain trying to solve some formulae that I will need to implement into a program I'm making. The program is based around statics of a particle, as in that all forces acting on the ...
22 views

33 views

### Showing that one physics equation 'satisfies' another

Background: This is from a Physics 2 Lab. The equations come from a circuit that has a resistor and a capacitor I'm given these two equations $V - \frac{dq}{dt} R - \frac{q}{C} = 0$ <== Eqn(2) ...
52 views

### Simulating a rocket in Matlab

I want to simulate a rocket. I found this code in a book. For the past two days I have been trying to understand it. For instance there is a line: ...
37 views

### Neumann condition and Dirichlet condition at the same point

I am studying heat equation on a 1-D bar. We now that Neumann conditions at both ends leads to a singular matrix (for finite element methods) in equilibrium. Adding an initial condition can lead to ...
76 views

41 views

147 views

### Very confused on fluid flow question

I am very confused on how to solve the following problem: If $2 \pi m$ represents the volume that is ejected per unit of time per unit length of the $z$ axis, obtain the velocity $v(r)$, ie the line ...
21 views

### Kinematics initial velocity [closed]

A grape is tossed straight up in the air and caught in the mouth. if the mouth is 1 foot higher than the point where the grape is released in the grape enters the mouth at 25 ft./s what was the ...
34 views

This is the problem: Let $t$ be the time it takes an object to fall $x$ feet. The kinetic energy of a ball of mass, $m$ dropped vertically $x$ feet is $E = {1 \over 2} m v^2$, where v = $h'$, and $h =... 0answers 19 views ### Identity in continuum mechanics For a problem in the textbook I am reading, I need to prove that$\int_Vw_{i,j}v_jdV = \int_Sw_iv_jn_jdS$, where$S$is the boundary of the volume$V$,$v_i$is the velocity vector field of a ... 3answers 74 views ### Falling objects - finding the speed [closed] I am trying to work out how fast water will be falling by the time the water hits the ground. If it starts 100m high how fast would it be travelling and why? With the acceleration because of gravity ... 0answers 39 views ### Result from derivatives seem inconsistent I'm working on a physics problem that looks like this For some context we have a person on his sled represented in our first term. The second term represents the velocity of a stone thrown backwards ... 1answer 35 views ### Questions on energy conservation of the wave equation I'm reading this book. In Ch. 3.4, it studies the wave equation$u_{tt}=c^2u_{xx}$with BCs$u_x(0,t)=0,\,u_x(L,t)=0$, and ICs$u(x,0)=f(x),\,u_t(x,0)=g(x)$. The total energy of a string is the ... 2answers 65 views ### On the existence of a point in the plane where repulsive central forces exerted by$ n $fixed points cancel This is a physics-inspired question. In what follows,$ \alpha \in (1,\infty) $is a fixed constant,$ n \in \mathbb{N} $a fixed integer$ \geq 2 $, and$ [n] \stackrel{\text{df}}{=} \mathbb{N}_{\...
Let's say a particle's velocity is modeled by $v(t)=\sin(t)$. Therefore, assuming the particle starts at position $0$, it's position $x$ can be modeled by $x(t)=\cos(t)$. The total distance traveled ...
A motorboat going downstream overcame a raft at a point A. $T$ = $60$ min later it turned back and after some time passed the raft at a distance $l$ = $6$ km from the point $A$. Find the flow velocity....