The description of the movement of bodies by their position, velocity, acceleration (and possibly higher time derivatives, such as, jerk) without concern for the underlying dynamics/forces/causes.

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0
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3answers
29 views

What was the motivation behind the work formula?

Surely there must be a reason we decided to use this as a metric for mechanical energy.How was it developed and what made it more acceptable than other work formula candidates (Like force over time, ...
2
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6answers
815 views

Why is momentum conserved (or rather what makes an object carry on moving infinitely)?

I know this is an incredibly simple question, but I am trying to find a very simple explanation to this other than the simple logic that energy is conserved when two items impact and bounce off each ...
1
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3answers
521 views

Determine resultant velocity of an elastic particle-particle collision in 3d space

So I have two particles that have collided in 3 dimensional space. I want the particles to rebound off of each other in an elastic manner. How do I determine the resultant velocity vector if I know: ...
-1
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0answers
32 views

It is possible to have a situiation in which $|\mathrm{d}v/\mathrm{d}t|$ is not zero but $\mathrm{d}|v|/\mathrm{d}t$ is? [on hold]

Please explain the following in detail: It is possible to have a situation in which $\displaystyle\biggl\lvert\frac{\mathrm{d}\vec{v}}{\mathrm{d}t}\biggr\rvert\neq 0$ but ...
0
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1answer
23 views

Minimum turning circle of an accelerating spacecraft

I think I've worked this out, but my maths/physics knowledge is far from perfect, so I'd love confirmation that it is correct. Basically, from $v =\omega r$ and $a_c = v^2 / r$ (where $\omega$ is ...
0
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3answers
46 views

Does a flying bullet get KE from gravity?

A projectile P is shot horizontally at 9.8 m/s from a height of 4.9 m, considering no air friction, after a second it will have v = 9.8 m/s on the x-axis and v = -9.8 on the y-axis. Because of ...
9
votes
5answers
2k views

If the earth is in constant motion then why do we say that an object is in a state of rest?

I got this question as my physics class homework for tomorrow. Anyone please help me out. If Earth constantly rotates and revolves, then how can we call an object in a state of rest?
9
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4answers
3k views

Why does the sun make me feel warm?

For a while I thought that the reason I felt warmth from the sun was because my skin was being hit by photons, but then I realized that photons also hit me when I take an X-ray, but I don't feel any ...
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0answers
13 views

Kinematics-Motion in one Dimension [on hold]

A man is standing on top of a building 100m high. He throws 2 balls vertically, one at t=0 and the other after a time interval(less than 2s). The later ball is thrown at a velocity of half the first. ...
-3
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0answers
16 views

Kinematics Question: Velocity and Acceleration Polygons [on hold]

I think I've been doing too many of these without much rest because I am stumped. The Curved slider mechanism is what is confusing me: Dimensions of a simple 2-bar linkage are given in the attached ...
1
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2answers
78 views

Motion of a rigrid body: Why is motion only a compostition of two forms: rotation and Translation?

If you are in a 2-D space the motion of any rigrid body is composed of 2 different things, namely rotation and translation. If you are in 3-D space the motion of any rigrid body is also composed of 2 ...
-3
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0answers
14 views

Kinematics-Motion in 1 dimension [on hold]

A motor car moving at 20m/s can not come to a stop in less than 3s while for a truck this time interval is 5s. On a highway the car is behind the truck both moving at 20m/s. The truck gives a signal ...
0
votes
0answers
41 views

Object pursuing exactly toward an uniformly moving object, with a twist

A friend of mine asked me about a problem he faced in an exam, but I happen to be rusty on this and can't seem to even understand it's implications, nevermind solve it. At $t=0$ an object A in ...
-3
votes
0answers
16 views

Controlling the flow of powder from a container, based on grams selected [on hold]

was wondering how you would control the flow of powder from a container (with a small cylindrical dispenser at the bottom). The container is filled with powder. As the container drains, less ...
1
vote
2answers
57 views

Projectile motion of Golf ball- Can projection height be calculated just from initial velocity and travel time? [on hold]

A Golf ball projected with a horizontal velocity of 30 meter per second and takes 4 second to reach the ground. Calculate the height the golf ball was projected from. Calculate the magnitude of ...
3
votes
2answers
139 views

Intepretation of area under velocity-time graph for a bouncing ball

A typical velocity-time graph for a bouncing ball is shown below. I understand that the ball starts from rest at $t=0$, then it accelerates downwards and hits the floor at time $t_1$. Between time ...
1
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2answers
238 views

Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...
0
votes
0answers
27 views

River Boat Problem with a Twist [on hold]

I am trying to solve the following river boat problem . A river of width w is floating such that the stream velocity varies with y as $v_R=v_0(1+(\frac{\sqrt 3 - 1}{w})y)$ where y is the ...
2
votes
2answers
55 views

Does deceleration (or negative acceleration) feel like acceleration?

This may seem like a dumb question, but I'm having a hard time trying to intuit the answer. The question is in relation to Einstein's famous thought experiment which says that it is impossible for a ...
2
votes
3answers
161 views

Is there an intuitive explanation of the work formula?

Upon learning calculus, I decided it was time to derive all of classical mechanics to give myself a good understanding of physics. What I found was that, while trying to do so, I would need some ...
1
vote
1answer
170 views

Magnitude of the average velocity vector (not the average speed)

Thank you ahead of time for taking to look at this. For this following problem we were given an answer however I am almost positive the given answer is wrong. It doesn't even make sense. So here is ...
-1
votes
0answers
12 views

Does driving forward and backward a car with the front wheel bending to the rightmost cause the car to rotate along the same circle? [closed]

When driving a car with the front wheels bent to the rightmost, will the car rotate clockwise along a circle? When driving in the same way except now backward, will the car rotate along the same ...
0
votes
1answer
43 views

Why do systems with a fixed gear-ratio still use gears?

From my understanding, there are two uses of a gearing system: to change the speed of output rotation (trading it with torque), and to change the axis of rotation. Now, in a car, for example, it is ...
0
votes
4answers
122 views

Why Do Objects move?

Let's imagine a block resting on horizontal table. When We apply a force which is greater than frictional force it moves. But why does this happen? Why can't friction withstand any force? As we know ...
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votes
0answers
39 views

Check ym WORK ( average velocity freefall and kinematics [closed]

A car is accelerating in the +x direction at 2seconds the car is 100m from the starting point. after an additional 5 seconds it is 1.5 km from the starting point. a. Determine the average ...
0
votes
3answers
73 views

How can Kinetic energy formula and the Work formula be derived without assuming the other to be true?

After searching how to derive the formula for Kinetic energy, I found that most derivations required the use of the "work" formula. After searching how to derive the work formula for a bit, I found ...
0
votes
0answers
10 views

can I move electromagnetic items in a plane at any direction? [closed]

Lets say we have some balls or other shapes that can be electromagnets (with the relevant electrified coils etc). I want to place stationary electromagnets at the edges of their plane and generate a ...
0
votes
1answer
49 views

When will the velocity of a particle be perpendicular to it's initial velocity?

I am learning kinematics with vector analysis. I was given the position equation:$\mathbf{r} = 10t\hat{\mathtt{i}} + (20t-5t^2)\hat{\mathtt{j}}$. It asks me the time when the velocity of the particle ...
1
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4answers
47 views

Car Crash Scenario [closed]

Two vehicles travelling at 80mph in the same direction. Vehicles are directly behind each other. 12 meter distance between them. Front door of car in front rips of and hits the front window of the ...
1
vote
2answers
54 views

Kinematics Question AP Physics [closed]

A motorcycle officer hidden at an intersection observes a car driven by an oblivious driver who ignores a stop sign and continues through the intersection at constant speed. The police officer ...
0
votes
1answer
38 views

Can avg. Vel. be zero in uniformly accelerated straight line motion?

A particle moves in a straight line with constant acceleration. The average velocity of this particle in an interval is zero. According to me it may become possible when velocity of particle is in ...
2
votes
1answer
115 views

General motion of a cone on an inclined surface

Suppose that a solid cone is placed horizontally on an inclined surface and is initially at rest. How will the cone move when it starts motion due to its weight? I know that its motion depends on the ...
0
votes
1answer
107 views

Relativistic Kinematics - 2-Body Particle Decay

Consider the scenario where a particle of mass $M$ decays into two lighter particles of mass $m_1$ and $m_2$. In the center of mass frame (i.e. $\mathbf{p}_1$ and $\mathbf{p}_2$, the momenta of the ...
14
votes
7answers
3k views

Flat throw vs 45 degree throw of a ball

Why does my sports coach tell me that when I'm fielding I should throw the baseball 'flat' to get the maximum distance? I thought from physics that you get the most distance from throwing at a 45 ...
0
votes
2answers
83 views

Convert an equation for acceleration into one for velocity

A sledge is pushed in a straight line. Assume surface is smooth. When the sledge is x distance away from the start the magnitude of its acceleration is given by $0.08e^{-4x}$ and is going in the same ...
1
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1answer
39 views

Nonzero acceleration is compatible with $d|\vec{v}|/dt=0$; why is the reverse not true?

It is possible to have change in magnitude of velocity w.r.t time to be zero and magnitude of acceleration to be non zero, $$\frac{d|\vec{v}|}{dt}=0 \quad \left| \frac{d\vec{v}}{dt} \right| \neq 0\, ...
11
votes
3answers
620 views

Is acceleration an average?

Background I'm new to physics and math. I stopped studying both of them in high-school, and I wish I hadn't. I'm pursuing study in both topics for personal interest. Today, I'm learning about ...
1
vote
3answers
96 views

Find time-parametrization given path and speed of a particle

Consider a particle in two dimensions with position vector $r(t)=<x(t),y(t)>$ and the shape of the path is described by a function $y(t)=f(x(t))$ (Thus $r(t)$ is a parametrization of $f$ with ...
0
votes
1answer
68 views

Problem conserving 4-momentum at CoM frame in an inelastic collision [closed]

I am confused about the case where mass is not conserved in a collision (not due to relativistic factors). The center of momentum (CoM) frame is not the same before and after the collision. Let's ...
0
votes
2answers
32 views

Distance traveled from displacement

I am currently reading a book called Physics for Scientists and Engineers by Serway. While reading the chapter about 2-dimensional kinematics, I asked myself a ...
0
votes
2answers
64 views

Energy in the Relativistic COM Frame

I have been taught that in Classical Mechanics, the total energy of a system of two particles in the Centre of Mass Frame is given by $$ E_\mathrm{total} = \frac{1}{2}MV^2 + \frac{1}{2}\mu v_r^2 $$ ...
0
votes
2answers
114 views

Changing directions with a constant speed?

I'm currently working on a problem in which an object's speed remains the same, but it experiences a change in direction after some time. I'm fairly sure it experiences an acceleration in order to ...
0
votes
1answer
38 views

Initial Velocity and Brakes [closed]

Mathematically investigate and derive a theoretical relationship between a vehicle's initial velocity (the dependent variable) and the length of its skid marks (independent variable). ...
0
votes
1answer
36 views

rolling a coin or a riding a bicycle [duplicate]

Why somebody riding a bicycle keeps balance and doesn't fall left or right, while is prone to falling when the bicycle stops. One force (to front) shouldn't affect in any way balance left/right. I ...
0
votes
1answer
122 views

Inclined plane, circular motion and the friction

Suppose we have a cylinder on an inclined plane of mass $m$ and radius $R$ moving without sliding (so that $\varepsilon = a/R$). Why is the friction $F$ causing the circular motion sometimes lower ...
0
votes
2answers
156 views

Projectile, air resistance and wind

So for my school project I am working on a projectile simulator and air resistance. So I have looked at this. Equations for an object moving linearly but with air resistance taken into account? ...
1
vote
3answers
148 views

What acceleration to use in this problem?

A balloon starts rising from the ground with an acceleration of 1.25 m/second square. After 8 second, a stone is released from the balloon. Find the time for stone to reach ground, distance ...
0
votes
1answer
30 views

the final velocity non-constant acceleration

I'm not sure if my problem was asked before, but if so, a simple link to the answer would be appreciated. Basically I've recently seen videos about spud cannons that use compressed air and it got me ...
0
votes
1answer
39 views

Explanation about friction force directions of two moving bodies in contact

can someone explain me why in this scenario (picture below) we have a friction force Ftr12 in the same direction as movement (left part of the picture, case 1 ) and how these directions of friction ...
4
votes
2answers
285 views

Projectile motion maximum distance to origin

Is there an elegant or easy way to derive the maximum distance from the origin to a point of the parabola created by projectile motion (assume initial position is the origin)? Other than ...