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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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: ...
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3answers
176 views

Why is the constant velocity model used in a projectile motion derivation?

I was re-studying university physics last week, I'm now in the chapter about kinematics in 2 dimensions and specifically the one treating projectile motion. In page 86 of his book (Serway - Physics ...
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2answers
612 views

Monkey and tree - projectile motion

The famous scenario: A hunter is trying to shoot a Monkey hanging from a tree. However, this question doesn't mention the monkey jumping down from the tree or trying to escape. (The hunter uses a ...
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5answers
2k views

How a spacecraft travelling near light speed avoid asteroids?

How would a spacecraft traveling near light speed avoid a (relatively dense group of) asteroids? Or suppose such spacecraft is designed, how would the physics work for steering it inside such a ...
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5answers
3k views

Zero velocity, zero acceleration?

In one dimension, the acceleration of a particle can be written as: $$a = \frac{dv}{dt} = \frac{dv}{dx} \frac{dx}{dt} = v \frac{dv}{dx}$$ Does this equation imply that if: $$v = 0$$ Then, ...
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1answer
110 views

Ball flying towards me - Newton's third law is violated?

I was trying to answer the question of the flying ball here on the basis of Newtons third law and Momentum conservation. Here is what I have tried. Lets take $m_1$ (the ball) hits $m_2$ (the man). ...
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2answers
477 views

Gas viscosity at high pressure, high temperature

EDIT 1 PER COMMENTS I am wanting to model nitrogen gas viscosity as a function of pressure and temperature OR learn of an existing equation that models nitrogen viscosity for the pressure and ...
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5answers
9k views

How can an object with zero acceleration move?

My physics text has a problem in which it is said that a person moves a block of wood in such a way so that the block moves at a constant velocity. The block, therefore, is in dynamic equilibrium and ...
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1answer
152 views

Circular motion - is average velocity enough to tell?

If I knew the exact value of constant centripetal force and the average velocity of an object travelling around a circle for time $t$, would that be enough information to determine the final positon ...
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1answer
33 views

kinematics: parabolic movement [closed]

How does the formula $ax^2$ is affected by the angle and the power of the launch of, let's say, a cannon ball, (regardless of its mass)? I am trying to create a simulation, and everything I have to ...
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2answers
61 views

How does the object at constant speed pass the accelerating object?

A car starts from rest and move with constant acceleration of $4\frac{m}{s^2}$ and at the same time a motorcyclist moving with a constant speed of $36\frac{km}{hr}$ overtakes and passes the car. ...
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2answers
36 views

Finding equation for exponential deceleration

Let's say my ship's velocity during deceleration phase is given by: $$ v(t) = v_0 \exp(-k t) $$ where $v_0$ is the speed at the time of starting deceleration and $k$ is arbitrary constant. My ...
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3answers
76 views

How to find stopping distance of a car? [closed]

I am trying to calculate minimum stopping distance of a car once the brakes are applied. I know the velocity at braking instant, i also know the distance from the obstacle. I found out that $$ d = ...
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3answers
33 views

Time taken for a body to reach a velocity of sqrt(a) from 0 under an acceleration a? [closed]

Lets say body starts from rest and would like to attain a velocity of sqrt(a) , where a is the acceleration (constant) of the body. By laws of motion we get t = 1/sqrt(a) which in the case of a --> ...
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1answer
291 views

Can the equations of motion be used for both instantaneous and average quantities?

I have three equations of motion: $$v = u+ at , $$$$s = ut + \dfrac{1}{2} at^2 , $$$$ v^2 = u^2 + 2as.$$ Can I use them for both finding instantaneous and average quantities? Suppose I want to find ...
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3answers
139 views

My physics teacher gave us this equation $v= -3 +3t$

She asked us if the body was accelerating or slowing down, and I immediately said that it was accelerating (because the $a=3>0$). Then she said that I was wrong because the direction of the ...
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2answers
45 views

Uniformly Accelerated Motion question

A ballast bag is dropped from a balloon that is 300 m above the ground and rising at 13 m/s. For the bag, find the maximum height reached. Now the book gives me this answer - $V_i$ = initial ...
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2answers
3k views

Proof of centripetal acceleration formula ($a_c = \frac{v^2}{r}$) for non-uniform circular motion

The formula for centripetal (radial) acceleration is well known, and there exist many proofs for it: $$||a_c|| = \frac{||v||^2}{r}$$ However, all the proofs I've seen rely on the fact that it is ...
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1answer
44 views

vector and position and acceleration [closed]

I really need your help with two problems. Consider a moving object that can be described by the position function r(t) = [(8.00m/s )t-[( 4.50m/s^3 )t^3 ]î +(− 2.00 )t^2+10.0m]ĵ In unit­vector ...
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1answer
36 views

Need help with acceleration question? [closed]

I don't understand how to solve this question involving two constant accelerations.
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2answers
133 views

Animating an Acceleration Vector - Acceleration of object on a crested path in gravitational field

So I was reading in Chapter 3 of my textbook, Sears & Zemanksky's University Physics with Modern Physics by Young and Freedman, 13th Edition, and the discussion took us to a definition of the ...
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3answers
483 views

Does a heavy body move with the slightest force on a frictionless surface?

If I apply horizontal force on a body resting on the ground, my force will be opposed by the frictional force and the body will accelerate at the point where my force exceeds the force of friction = ...
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2answers
18 views

Kinetic energy on macro and micro situation

I just have this random question in my mind. If you drop something in deep space, and it falls due to a gravitational pull. As it's falling, its kinetic energy increases. I just wonder, is the average ...
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0answers
38 views

How velocity progresses over time with a non-constant acceleration? [closed]

A $0.25\text{ kg}$ sphere of radius equal to $0.07\text{ meters}$ is dropped from rest from the top of a building. Granted that it will not hit the ground before, when and after what distance ...
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1answer
55 views

How does angular momentum affect the trajectory of a projectile?

I am thinking about a football thrown in a very tight, very fast spinning spiral. If the football is thrown upwards at a high angle, is it possible for the football to not turn over at the top of its ...
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1answer
76 views

Motion in the gravitational field along a trajectory [closed]

A point particle of mass $m$ is moving in the gravitational field along some trajectory which is described by the function $y=y(x)$, which is in a vertical plane and is continuous. Initial ...
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1answer
43 views

Can I use $(v_1+v_2)/2$ to find average velocity? [closed]

An object is traveling from a point $M$ to a point $N$ with a velocity $v_1 = 600 \,\rm km/hr$ and comes back with a velocity $v_2 = 400 \,\rm km/hr$. What is the average speed of the object? Can we ...
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1answer
39 views

Speed of a river [closed]

I've got a problem (Sorry if it's too basic). It is: Going upstream in a canoe, the passengers throw an empty bottle. They keep rowing for 60 minutes, and move 2 kilometers upstream. They then start ...
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1answer
44 views

Minimum Distance for “Speed of Light Approach”

I tried to calculate the minimum distance between a planet and a test mass for the mass to attain the speed of light on colliding with the planet's surface if it were released from rest at the initial ...
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1answer
43 views

Motion in 2 dimentions relating $\delta x$ to $\delta y$ [closed]

In a self exercise i was trying to solve this users question what is the initial velocity if angle and range is given? My aim is 1) not to use the standard equations of motion but rather calculus; ...
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1answer
28 views

Definition of a symbol $s_{NN}$ appearing in particle physics

What is the meaning of $s_{NN}$ in particle physics? See e.g. here http://www4.rcf.bnl.gov/brahms/WWW/thesis/karabowicz_phd_thesis.pdf page 18 in the pdf. What is its relation to energy? I ...
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1answer
36 views

a question regarding relative velocity

"Consider a gravity-free hall in which an experimenter of mass $50~\text{kg}$ is resting on a $5~\text{kg}$ pillow, $8~\text{ft}$ above the floor of the hall. He pushes the pillow down so that it ...
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2answers
74 views

What causes the random movement of particles inside a conductor?

I'm reading about currents in electricity right now, and it was mentioned that even if there's no electric field inside a conductor, charged particles inside are still undergoing random movement. I ...
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8answers
539 views

Can velocity be an undefined quantity?

We have the image below displaying the uniform velocity by time-distance graph. At every point velocity is constant but what if distance and time both become zero as at origin in the graph is? The ...
2
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1answer
258 views

Is rate of change of velocity wrt distance and rate of change of velocity wrt time the same thing?

Is rate of change of velocity wrt distance and rate of change of velocity wrt time the same thing?If both are same can we define acceleration in the former way? Please explain using calculus.
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1answer
58 views

How to find the function of acceleration respect to time while having the function of acceleration with respect to velocity

As everyone know that the integral of acceleration respect to time will give the function of velocity respect to time. However, my question concern the different case when the function of a(t) is not ...
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2answers
48 views

Height of building [closed]

How would I find the height of a building? I have been given the initial velocity, the angle at which the object was thrown, and the landing distance. And I was able to successfully compute the ...
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1answer
446 views

Kinetic energy of an expanding sphere [duplicate]

In the study of Newtonian stellar structure, Weinberg (1972) writes The uniform dilation of a sphere with uniform density will give it a kinetic energy $$U=\frac{3}{10}M\dot R^2$$ I don't ...
2
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2answers
67 views

Hockey puck collision [closed]

I have a homework question in which a sticky hockey puck traveling at constant velocity parallel to the side of the rink strikes a stationary puck and sticks to it. The angels between centres at ...
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2answers
52 views

Can anyone kindly help me with these sign conventions?

Since I have some confusions with the sign conventions , I have finally drawn up the following conclusions . Plz check if the following are correct .... ( I have taken all motions directed upwards as ...
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3answers
173 views

Problem in deducing the equations of motion using indefinite integral

As we know, antiderivative or indefinite integral is the function the derivative of which gives the actual function. Let $F(x)$ be the derivative of $f(x)$ ie. the instantaneous rate of change of ...
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3answers
1k views

Does uniform circular motion occur in real life in a non horizontal plane?

I have a question about UCM, as I am studying it in my Physics course. I understand that Non-UCM experiences a tangential acceleration component, which is the result of changing speed along its ...
15
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7answers
5k views

How can kinetic energy be proportional to the square of velocity, when velocity is relative?

Let's start with kinetic energy (from los Wikipedias) The kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a ...
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0answers
36 views

Web utility for viewing $x$-$t$, $v$-$t$, and $a$-$t$ graphs

I'm wondering if there exists any utility on the web which displays $x$-$t$, $v$-$t$, and $a$-$t$ graphs for, say, a number of well considered example animations. The utility should allow pausing, ...
2
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0answers
60 views

Modelling an Inelastic Collision

I've attempted to model the inelastic collision between a moving mass and a large stationary object, e.g. dropping an ball on the floor, for analysing the approximate kinematics and heat dissipation ...
2
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1answer
22 views

How do I find the angle with respect to the ground that will cause a projectile launched from the origin to land at the origin? [closed]

Given an arbitrary non-zero constant horizontal acceleration (like a breeze perhaps), how would one find the angle with respect to the ground (x-axis) that will cause a projectile launched from the ...
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3answers
529 views

I am unable to combine two equations in kinematics

Sorry people, very basic kinematic stuff here. (1) Velocity: $$v=\frac{d}{t}$$ (2) Acceleraton: $$a=\frac{v_{f}-v_{i}}{t}$$ (3) Re-arrange acceleration: $$v_{f} = v_{i}+at$$ (4) Ok here is my ...
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1answer
42 views

Equation for Figuring out the Displacement for a Projectile at an Angle

I'm wondering if anybody can simply tell me if there is a simple formula to solve for displacement when you've been given the launch angle and initial velocity? See; http://is.gd/LpT1EA To some, it ...
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1answer
45 views

Necessity of the Notion of Work and Kinetic Energy

I've worked through many example problems in my college physics text in the section on kinetic energy and work. I noticed that if the desired quantity is velocity or force, they can be solved entirely ...
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1answer
56 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 ...