1
vote
2answers
21 views

Solving equation of motion with exponential friction term

My friend's kid asked me this question. I have no idea how to solve it since I have stopped calculating mechanics for about 15 years since I graduated from high school. The question is: A boat that ...
1
vote
1answer
76 views

Advanced kinematics problem regarding $F = ma$

I really need help with this problem. Thank you for your time. Question: Look at the figure below. Derive the formula for the magnitude of the force F⃗ exerted on the large block (mC) in the ...
0
votes
0answers
8 views

Convex and Concave Bridges forces [on hold]

What are the forces acting on a car when travelling in a concave and convex bridge?
0
votes
1answer
25 views

Two-block system acceleration when applying a force in the $x$ direction

Two blocks are connected by a light-weight string that passes over a friction-less pulley (a.k.a. Atwood's machine). Block # 1 (called $m_1$) hangs from the edge of a friction-less table. Block # 2 ...
3
votes
1answer
43 views

Calculating time to reach certain velocity with drag force

I was given a problem for homework where we needed to calculate the time for a falling object to reach a certain velocity when accounting for drag force. I did it by setting up acceleration as a ...
1
vote
0answers
34 views

How torque and friction cause wheel to roll

I apologize if this question has been answered before, but I did not find the explanation that I needed. If a torque is applied to a wheel situated on a frictional surface, what forces cause the ...
1
vote
0answers
46 views

Tension Problem: Solve for T for two sliding blocks connected by a string [on hold]

The problem: Two blocks made of different materials connected together by a thin cord, slide down a plane ramp inclined at an angle θ to the horizontal as shown in the figure (block B is above ...
1
vote
1answer
40 views

Static and kinetic friction [on hold]

Say you have block1 on top of block 2 and the whole system is accelerating toward the right at a certain acceleration. Due to inertia block 1 wants to move backward to the left so there has to be a ...
1
vote
2answers
29 views

Diagram of forces exerted on objects

Assuming that there is an interaction between 1 and 3 (they attract each other), what are the forces between 1 and 2? I know it is as if the force acts on a different body (1+2), but I want to know ...
0
votes
0answers
28 views

Where is the maximum center of mass so it doesn't fall over? [on hold]

I have some sort of barrow with brakes, which its deceleration due to the braking never makes the crate slide down: I have found it is $\mathbf{a} \leq g(\mu\cos\theta - \sin\theta)$ (note that it ...
1
vote
1answer
20 views

Calculate coefficient of friction from deceleration with and without conservation of energy

How can I solve the following problem? A block that moves at the speed of 120 cm / s keep going for 70 cm before stopping. What's the coefficient of friction between block and table calculated ...
3
votes
2answers
73 views

Why are some forces not included in the sum of forces?

I was given the following notes in class: 4.32 A skier of mass $65.0\text{ kg}$ is pulled up a snow-covered slope at constant speed by a tow rope that is parallel to the ground. The ground ...
-2
votes
0answers
14 views

Calculate the maximum displacement of mass 'm' body, when the system is released from rest at euqilibrium? [on hold]

Image Describes about a system at equilibrium, which consists of springs, pulley, and a body of mass 'm'.
0
votes
1answer
26 views

Horizontal distance covered by an object from an initial height to the ground

We are given: An angle $\theta$ with respect to the ground, its initial height $h_0$ and the final distance $d$. How can we find the initial velocity from this information? I tried a bunch of things, ...
3
votes
1answer
86 views

Could $\int (\ddot\phi + \mu\dot\phi^2)d\phi$ ever be negative? How to show it?

I am working on the following problem: Given a mass $m$ at rest at the base of an incline surface shaped like 1/12th of a circle with radius $R$. The mass is pulled up the incline by a rope that ...
0
votes
0answers
44 views

Projectile under quadratic air resistance force

So here's the problem background: A projectile of mass m is shot straight up with initial velocity $v_0$ and feels a quadratic air resistance force of the form $F = −kv^2$, where $k ≡ mg/u^2$. ($k$ ...
-4
votes
0answers
35 views

Position Vector confusion [closed]

I am having a little trouble understanding why the position vector r in calculating the $v_a$ is given by $225/\sqrt2$ (-i -j) If it is the position of C with respect to A shouldn't it just be $225$ ...
0
votes
0answers
18 views

Change in momentum [duplicate]

A cube has a side length of 20 cm. An atom in the gas moves around the cube as shown. It continually bounces off the four lateral walls of the cube. The atom has a mass of 6.6×10−27 kg. Because of the ...
-1
votes
0answers
18 views

Find $r$ and $\theta$ given orbital elements [closed]

Calculate $r$ vector and $v$ vector in AU and AU/TU respectively for the Halley's comet on September 12, 2014 given: 𝑎 = 17.9 AU 𝑒 = 0.967 𝑖 = 2.8274 rad Ω = 1.0210 rad 𝜔 = 1.9513 rad 𝑀 = 0 rad ...
0
votes
0answers
20 views

Determine radius, speed, radial and tangential component of velocity [closed]

I need help mainly with the first question. If you can solve also the second problem,I'd greatly appreciate it.
-2
votes
0answers
27 views

Particle Acceleration in three dimensions [closed]

So here is the problem I dont know how to approach it.
-2
votes
0answers
16 views

Find acceleration along normal and tangent [closed]

A small block can move in a straight horizontal line a along AB. Flash lights from one side projects its shadow on a vertical wall which has horizontal cross section as a circle. Find tangential & ...
1
vote
1answer
339 views

How fast must a torus spin to have a felt gravity? [closed]

Given a rotating torus (like a gyroscope or a rotary) with a radius of 1km, how fast must it rotate to have someone inside the torus feel normal gravity of 1G?
1
vote
1answer
65 views

Question about torque and center of mass [duplicate]

If a yo-yo's string is not attached to anything and the yo-yo is dropped, it is obvious it will fall at $g$. In this scenario, Tension of string = 0. If a yo-yo's string is attached to a cieling and ...
18
votes
5answers
4k views

Is this scene from the A Team explainable by Physics?

This scene (youtube link) from the movie The A-team, the four members are in the tank and its falling from the air, they fire the canon and it slows the tank from falling for a moment before falling ...
-2
votes
1answer
34 views

Projectile with air resistance [duplicate]

If you have a projectile with these variables. $x_0 = 1v_{0x} = 70, y_0 = 0, v_{0y} = 80, a_x = 0, a_y = -9.8$ I know how to plot these points with this equation. $$ x = x0 + (v_{0x})t + 1/2((a_x)t^2) ...
1
vote
0answers
20 views

Collision (work energy and power) [closed]

A ball is allowed to fall from rest on a horizontal floor from a height of 10m If there is 20% loss of energy due to impact then after one impact ball will go upto?
0
votes
1answer
120 views

From Paris to … London [closed]

(Excuse the pun in the title, couldn't resist) Paris and London are connected by a straight underground tunnel, as shown in the diagram below. A train travels between the two cities powered only by ...
0
votes
2answers
53 views

A spring with two masses in an inelastic collision

An ideal spring is attached to a wall, and the other end is attached to a mass $m$. The spring is initially compressed a distance $x$. After it is released, the mass collides with another mass $2m$ ...
0
votes
0answers
28 views

Calculus of variations applied to a rotating liquid

I thought I knew how to use calculus of variations, but then I started thinking about the problem of a rotating liquid and it confused me a great deal. It would be nice to hear your thoughts on the ...
2
votes
1answer
111 views

Add air resistance to projectile motion

I am given an initial x and y position and initial velocity and I was asked to graph the trajectory in 1 second intervals. This is what I have so far: If $x_0 = 1, v_{0x} = 70, y_0 = 0, v_{0y} = 80, ...
0
votes
0answers
32 views

Coriolis deflection:- is it 4 times if the object is thrown up, compared to a drop?

A particle is thrown up vertically with initial speed, reaches a maximum height and falls back to ground. Show that the Coriolis deflection when it again reaches the ground is opposite in ...
1
vote
0answers
54 views

Integrating with respect to time a double derivative $\ddot\phi + \frac bm\dot\phi = \frac{F}{mr}$ [migrated]

$$\ddot\phi + \frac bm\dot\phi = \frac{F}{mr}$$ I want to integrate this to get an equation for $\dot\phi(t)$ but I don't know how to integrate double derivatives. The answers say that the ...
-1
votes
1answer
33 views

Decelerating car [closed]

A car crashes into a immovable barrier at 60mph. (a)If the front-end of the car crumples a distance of 1.5 m in the collision, what is the deceleration experienced by the occupants? (Express your ...
2
votes
1answer
44 views

Weight held by jet stream of water

Consider a bucket of weight $W$, held in air by a jet stream of water from the ground (moving vertically upwards) at height $h$. The water is fired from the ground at the rate of $\mu$ (units ...
2
votes
1answer
154 views

Is work is equal to $mv^2$ (without $\frac{1}{2}$)?

I was trying to come up with an equation for work that doesn't include time, because I don't know time. Here's what I did: $$ work = Fd = mad = m{v\over t}d = m{v\over\left({d\over v}\right)}d = ...
1
vote
0answers
67 views

Show that the profile of the hill is a cycloid [closed]

I'm struggling with this problem: From George Simmons_ Differential Equations I've tried different things and I showed that the $x$ component and the $y$ component of the shadow should move with ...
4
votes
3answers
110 views

Different results to a basic question ( Newton's law and perservation of momentum)

Trolley with mass of $m_0=1 \ kg$ is moving without friction on the railway track. It is raining so there is a constant mass flow of water $\Phi_m=0.1\ kg/s$. Constant force $F=0.1 \ N$ is ...
0
votes
1answer
64 views

A moving inclined plane with block problem

I'm trying to solve for a challenging problem : a moving inclined plane with a block I want to solve for the acceleration components for the block and the plane and the normal force acting on the ...
0
votes
2answers
49 views

equivalent spring constant for a drum floating in water

If I have a drum floating in water, how do I find the equivalent spring constant? I know that the water has density $\rho$, the drum has diameter $d$ and height $\ell$, and the positive direction is ...
5
votes
2answers
342 views

The acceleration vector of a simple pendulum

In this picture the acceleration vector $\vec{a}$ points upward when the pendulum is halfway Click To see animated GIF But according to this picture, the force acts tangentially: Which means the ...
1
vote
1answer
67 views

An oscillating skateboard

A half pipe of a skateboard park consists of a concrete trough with a semicircular section of radius 5m, I hold a frictionless skateboard on the side of the trough, pointing down toward the bottom and ...
1
vote
0answers
34 views

Length of the missing part [closed]

I have got a very interesting question. A car is driving this way on the picture down. In the looping is a missing part. The radius of the looping is r = 40cm. The car starts at the height h = 3r. If ...
0
votes
1answer
39 views

At the instant of release of an object from rest. Is the only force that can act its weight?

Q3 from a mechanics exam past paper: I can do parts i) and ii) but for iii) in finding the angular acceleration, i used $C=I\alpha$, where $C$ is the applied couple or torque, $I$ is the moment of ...
3
votes
1answer
48 views

Relationship of multiple particles under collision [closed]

Consider 3 particles. All 3 particles travel along the x-axis. The 1st particle possesses some mass, m, and its initial position is somewhere on the negative x-axis. It has some (positive) velocity ...
0
votes
0answers
14 views

Relationship of multiple particles under collision [closed]

Consider 3 particles. All 3 particles travel along the x-axis. The 1st particle possesses some mass, m, and its initial position is somewhere on the negative x-axis. It contains some (positive) ...
3
votes
0answers
44 views

How to find tension in the cantilever brakes?

In the left side example of cantilever brakes, how do I find the tension in strings DE and DC, in terms of T. According to me applying force balance equations, horizontal and vertical forces should ...
1
vote
2answers
99 views

Force Diagram for K&K 2.13 [closed]

I have been (independently) working on Problem 2.13 in Kleppner and Kolenkow's An Introduction to Mechanics and come to an answer which conflicts with the hint the authors provided in the book. The ...
1
vote
2answers
117 views

How can Excel be used to model the flight of a rocket? [closed]

Firstly, sorry for any silly mistakes or improper use of this website - this is my first time using it! I am trying to use Excel to model the flight of the Apollo 11 Saturn V rocket using the real ...
0
votes
4answers
76 views

Find a central force given the orbit

I've been trying to solve the following problem for a long time. Let's consider a particle of mass $m$ in $\mathbb{R}^3$ with polar coordinates $(r,\theta,\phi)$. The particle moves on the orbit ...