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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45 views

What are the major differences in group-skydiving as opposed to “single” skydiving?

Surface area/the cross-sectional area is greatly increased, so my thinking is it should decrease terminal velocity as well as a couple of other factors. But mass changes too (since there would be more ...
2
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0answers
42 views

Searching for acceleration to minimalize path or time

I am thinking about motion of one point starting from $(0,0)$ and with velocity $\mathbf{v}(0)$. What is the acceleration $\mathbf{a}(t)$ with condition $|\mathbf{a}(t)|<M$ that minimalize ...
4
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3answers
382 views

Newton's First Law of Motion; Empirical Aspects

Newton's first law states that in an inertial frame, a body at rest continues to be at rest, and a body in constant rectilinear motion continues its motion, unless an external force is applied upon ...
3
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1answer
120 views

How to interpret $t^2$? [closed]

I can't think of the meaning of squaring the Time (multiplying it by itself). It makes sense in Mathematics. But how can you figure it out in nature (or physics). As an example, the formula ...
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2answers
84 views

Solving distance with acceleration and velocity given and getting two different answers using two different equations [closed]

Frictional forces from brake pads are responsible for stopping an automobile. A car is moving at $35.0 \:\mathrm{m/s}$. If the car's brakes are capable of generating a deceleration rate of $6.00 ...
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1answer
87 views

Work done: kinetic energy or area under F-ds curve?

Starting from $$F=ma = m \frac{dv}{dt} = m \frac{ds}{dt} \frac{dv}{ds} = m v \frac{dv}{ds}, $$ leads to work done = integral of F.ds = integral of mvdv = change in KE. Suppose a variable force is ...
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4answers
2k views

When does acceleration due to gravity equal positive/negative? [closed]

For example a projectile is launched at an angle. What would $a$ in $y=vt +.5at^2$ be? Let's say I choose up to be positive. How do you not confuse yourself whether to use positive or negative $a$?
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2answers
119 views

Is it possible for a moving body to have no kinetic energy? If yes, then how? [closed]

An object which is moving relative to your coordinate system has kinetic energy in that coordinate system; it does not have kinetic energy in a coordinate system which is stationary relative to the ...
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1answer
166 views

Relating momentum fraction to rapidity in a high-energy collision

It's a well-known result in particle physics that in an underlying interaction like this: assuming $p_0^-,p_{0\perp},m_0\ll p_0^+$, $m_1$ and $m_2$ are small, but $p_{1\perp}$ and $p_{2\perp}$ are ...
2
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1answer
112 views

Predicting balls's movement in well due to fluid flow

I am a total newbie in fluid dynamics. In one of my experiments/open project, my experiment setup is as below: a small ball sits in a circular well (has mass density a bit heavier than water), with ...
2
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0answers
74 views

Heads, Tails… Edge?

No Nobel prizes at stake, but just an idle thought and an idle question. How could one calculate the probability of a flipped coin landing stable on its edge, instead of heads or tails? I assume ...
2
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1answer
118 views

From acceleration to displacement

Hi I am a major in Computer science and this question should be really easy for all the physics geniuses here: I have a set of data points from an accelerometer on a moving object that basically ...
2
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1answer
76 views

Curvature of a particle move

I'm simulating a particle movement following a normal distribution. How this is done: My particle has a constant speed v and every step the particle move, I ...
1
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1answer
139 views

If a car appears in horison and within 2 seconds passes you by, whats the speed it's doing?

While watching the first 4 seconds of driving at 745 km/h is ludicrous from any angle wondered If we knew the curvature of the Earth in a "flat" desert, what would be the speed of the car? ...
0
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2answers
131 views

How many equations are there to calculate distance?

I am an app developer and I am trying to build a physics app to calculate distance based on the quantities the user gives. for example if the user gives initial speed, time and acceleration, using ...
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1answer
90 views

Projectile at an angle. Finding the angle using conservation of energy [closed]

Ball is thrown at an angle α and at the highest point it's potential and kinetic energy are the same. Find the angle. Use the law of energy conservation. What the professor wanted $mV^2/2 = 2* ...
0
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1answer
128 views

How to calculate the horizon line of a satellite?

I need an equation to calculate a list of Earth-centered, Earth-fixed (ECEF) XYZ coordinates on the earth that represent the visibility limit of satellite given its ECEF XYZ coordinates. For any ...
1
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1answer
87 views

Prove the relation between relative velocity ,momentum and energy

In Chapter 8 of F.Mandl's book Quantum field theory, during the derivation of the differential cross section, the following relation is used: $$E_1E_2v_{rel}=\sqrt{(p_1p_2)^2-m_1^2m_2^2} \,\, ,$$ ...
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2answers
690 views

Does a force really act on a body during a collision?

Consider two bodies A(black) and B(red) having equal mass. A is moving at a constant speed towards B, which is stationary. At certain point of time, they collide elastically, $\therefore u_{A}=v_{B}$ ...
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2answers
125 views

Kinetic Theory of Gases: Why do gas molecules have translational motion?

The title pretty much asks the question. I was reminded of the Kinetic Theory of Gases recently and I am puzzled as to why gas molecules would have any translational motion. Is it because collisions ...
1
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0answers
40 views

Describing the motion of a point-mass [closed]

Consider a point-mass moving around a fixed point on a circle with radius $r$ with constant angular velocity $\omega$. At a certain moment of time, the connection is removed, and the point-mass flies ...
0
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1answer
32 views

cross over to another object that has same height with our last position, is that really possible?

I have got confused with this. Well..In that picture, lets say the height is 8m, and the car moves and going to cross over to another object that has the same height with its last position..my ...
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0answers
138 views

Do human body parts like hands or legs move with uniform acceleration?

So, is this true? I mean, does a movement by hand or leg make uniform or constant acceleration?
2
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1answer
75 views

Different results for displacement using different Kinematics equations

We drop an object from a height. It displaces a distance $L$ in the $\vec{y}$ direction. So: $$ L = \frac{1}{2}at^2 $$ Or: $$ v^2-v_0^2 = 2aL \rightarrow L = \frac{v^2}{2a}$$ How much would the ...
4
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2answers
261 views

Does a tire need to slip to generate force?

Recently, I have been doing some research on racing and tire modelling. While I was doing this, I encountered many curves like those shown below. While I understand the need of slip angles to ...
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3answers
677 views

Speed of an object in air versus in vacuum

Okay, imagine that you are shooting a rocket down a tunnel that is 60 miles long and the rocket is travelling at 60mph, so the rocket should reach the end of the tunnel in a hour, right? Yep, in an ...
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3answers
519 views

What would happen if an unstoppable force hits an immovable object? [closed]

I realize that the question a rather large paradox, but I do wonder if such a thing were true what would happen, assuming that neither of these "objects" can be destroyed by each other?
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7answers
37k views

What does the magnitude of the acceleration mean?

I am a little confused as to what the magnitude of acceleration is and what it means.
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2answers
222 views

How to know the Direction of the Acceleration Vector?

If the exercise doesn't give you the direction, how to know the correct one? Sometimes I assume its to the right and it was actually to the left, and I get everything wrong. Example here: How can I ...
0
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1answer
89 views

Is velocity always tangential to trajectory?

So I was doing an exercise and they find find the angle between the tangential of trajectory and the vertical I was stuck but then I read in a site that the velocity is ALWAYS tangential to the ...
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0answers
20 views

temperature and velocity exchange

So there is a relation between total temperature and velocity of a fluid. In an adiabatic flow what determines how much one property (velocity or temperature will change)? I know the equation. But ...
1
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1answer
30 views

Computing the Initial Velocity of an orbiting body

I'm working on a simulation program that replicates the movement of planets around a large celestial body (the sun). This is a three dimensional simulation that uses vectors. At present, I'm ...
0
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2answers
60 views

Adding rotations onto a vector

I have a vector with spherical co-ordinates $(r_1,\theta_1,\phi_1)$, then I want this vector to be rotated by $\theta_2$ $\phi_2$ spherical angles but I cannot figure out how. I have tried using the ...
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3answers
53 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
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2answers
33 views

About using screw in air compression and air Engine [closed]

I want to use screw to build compressed air engine, as following image As I designed, this screw rotate in a tube My Question is: How successful this idea? Note: If this question not related to ...
0
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0answers
24 views

How does momentum effect velocity? [duplicate]

I'm in AP physics and we haven't even covered this yet so sorry if my question seems strange... I know $p = m v$, However right now I am writing a 2D physics engine and I am having some trouble with ...
0
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1answer
51 views

Kinematics problem regarding motion of a particle [closed]

A particle of mass m moves on the $x$-axis as follows: it starts from rest at $t = 0$ from the point $x = 0$, and comes to rest at $t = 1$ at the point $x = 1$. No other information is available about ...
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votes
1answer
34 views

How do you measure the acceleration of two objects with different masses? [closed]

I would like to know how to measure the acceleration of two objects with different masses...(and the formula that's used.) For instance a steel ball that, say...weighs 67g and a wooden ball that ...
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votes
3answers
75 views

How to account for inertia in kinematics?

Alright, I'm only in AP Physics and I asked my teacher and he couldn't help me... I'm making a 2D physics engine and I'm having problems when it comes to gravity between objects and I think its ...
0
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1answer
51 views

What is the movement of the material point? [closed]

The parametric formulas for movement of a material point are: $x(t) = A \sin (kt)$ $y(t) = B(1 - \sin(kt))$ Describe the movement of the MP. That is the entire question and I can't find a ...
1
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0answers
36 views

Why we don't integrate intital velocity in body cast equation?

On this site I've found a formula for calculating the $x, y$ coordinates for a body throwed by an angle to a horizon. It looks like this: $$x(t) = V_0 t \cos(\alpha); $$ $$y(t) = V_0 t ...
0
votes
4answers
197 views

How is acceleration measured if there is change only in the direction of velocity & not magnitude?

The formal definition of acceleration is It is the measure of how fast the velocity changes with respect to time. Now, when the magnitude of velocity changes, acceleration $$\vec{a} = \frac{d ...
2
votes
2answers
644 views

Velocity of car down an Inclined Plane

I was learning to make a car game and came across this situation where my car is on an inclined plane. It's initial velocity is 0. Now, the problem is that my memory serves me this formula to ...
1
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0answers
34 views

Change velocity formula from a function of displacement to a function of time [closed]

I have this problem from my dynamics book and I can't figure out how to solve it. I've played around with all the formulas and asked a few friends who did the course in the previous years but I can't ...
0
votes
1answer
143 views

Finding acceleration and distance when velocity given

I am trying to do the following question for practice (it is an interview question), and I don't know if my methods and answer are correct. Given a velocity $v=2+3t^2$, find acceleration after 3 ...
0
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1answer
156 views

Does rotation increase mass?

If an object is rotated on its axis near the speed of light would its mass increase? Normally if the object was moving (in relationship to the Earth for example) I would agree that its mass would ...
1
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1answer
30 views

Minimum power to pull a sheet of paper [closed]

I'm trying to tackle a question in kinematics, but I miss something and don't know what. The question goes like this: Let a homogeneous pole of mass m be connected to ceiling and lean on the ...
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votes
3answers
213 views

Where does the force to stop a constant velocity object come from?

If a ball hits a wall at a constant velocity, it will slow down and eventually come to rest. Since the ball was at constant velocity, it was not accelerating, and so there was no force. Also, the ...
0
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1answer
93 views

Finding the Angle of Launch for a Cannon Projectile to Hit a Specific Point [closed]

A cannon with barrel length of $l$ was placed with its base at the origin $(0,0)$. A ball was fired with the initial speed of $v$ as it leaves the barrel at an angle of $\theta$ above the horizon. ...