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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5
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1answer
321 views

How to calculate the kinetic energy of supernova ejecta?

I believed I could use $0.5\times M_{ej} V_{ej}^2$, with $M_{ej}$ being the ejected mass and $V_{ej}$ being the velocity of the ejected mass. But I noticed in this and this that the the mean velocity ...
0
votes
1answer
43 views

Ways of finding average accelleration

So I had a little debate with a professor on a simple problem of motion (See section). It basically comes down to how to find average acceleration. I did some research and couldn't find a definite ...
0
votes
1answer
91 views

Average acceleration when more than two different velocities occur [closed]

Suppose a car travels at 5m/s north for 5 seconds, it then turn east and travel at 7m/s for 10 seconds, finally it turns north east and travel at 10 m/s for 20 seconds. What is the average ...
0
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1answer
101 views

Finding Acceleration Force of Gravity on Rotated Accelerometer

Is it possible to calculate the force of gravity on the $x$, $y$, and $z$ readings of an accelerometer if I know the rotation of the sensor? If so, how would I do this? Sorry if I am doing this ...
2
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3answers
271 views

Two runners on two different tracks

I got a question from a textbook, as follows. On two different tracks, the winners of the one-kilometer race ran their races in 147.95 seconds and 148.15 seconds. In order to conclude that the ...
0
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2answers
124 views

Problem finding the average velocity [closed]

Problem: A car travels along a straight line for first half time with speed of 40 km/h and second half time with speed 60 km/h. The mean speed of the car is__________. My answer: 48 km/h Why? ...
0
votes
1answer
211 views

Relative velocity of two cars [closed]

Two cars A and B are at $100\,\text{m}$ and $200\,\text{m}$ distance from the origin $O$ at time $t = 0$. They start simultaneously with velocities $10\,\text{m/s}$ and $5\,\text{m/s}$ respectively. ...
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1answer
96 views

Gravitational Potential Energy to Kinetic Energy

When a yo-yo is released from a height $h$, the gravitational potential energy is converted to kinetic energy. However, the yo-yo obviously has less acceleration than $g$, $9.8\frac{m}{s}$. This means ...
1
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1answer
296 views

Forces acting on a double pulley

In a double pulley system, if the mass of the object is 10 kg and the object is accelerating upwards at 2 m/s$^2$, what is the tension in the ropes? I figured the weight of the box is 100N and the ...
1
vote
1answer
93 views

Earth moving over the Sun instead of around [closed]

Let's say you are observing the movement of the Sun and Earth from very far away. After year 1, the Earth creates an orbital plane around the Sun. Since the objects in the universe induce forces of ...
0
votes
1answer
74 views

Deviation from 2D trajectory [closed]

I need to find out how far a ball is from the predicted trajectory in 2 dimensional space and I know the start and end position of the ball in both dimensions. Along with that I know the initial ...
1
vote
1answer
134 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 ...
0
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3answers
93 views

Perceiving travel speeds from different view points

Scenario: Two vehicles pass each other on a highway moving at 100km's an hour; from a stationary position beside the road you witness these cars pass each-other directly in front of you: from your ...
0
votes
1answer
261 views

What do negative times and negative distances represent in parametric projectile equations?

There are negative times and negative x and y distances in parametric equations; what do they represent? And is it possible to tell the object's speed, direction and acceleration from just a ...
0
votes
2answers
147 views

What moves an object? Momentum or Kinetic Energy? [duplicate]

What exactly makes an object move? Momentum is $\vec p= mv$ where $m$ is mass of an object and $v$ is the velocity of an object, and as a result of this when I fire a bullet the bullet may travel much ...
0
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1answer
259 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 ...
0
votes
1answer
46 views

Are Both figures correct? [closed]

Actually I am in high school I just want to confirm that whether two figures of this question possible: Question is : A car is moving along a straight line OP.It moves from O to P in 18 seconds and ...
-2
votes
1answer
52 views

Simple mechanics problem [closed]

I have no idea how to approach this problem I drew the diagram but that hasn't helped that much.
0
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2answers
453 views

Kinematic sign convention

For example, if I drop a ball from a $50$ meters building, then I will consider the ground is $0$ meter downward is positive ( which makes gravity positive, downward velocity positive, etc) so ...
-1
votes
1answer
696 views

Finding dv/dx when given x and v as functions of t [closed]

This isn't a homework question, I tried to word this as a physical problem and it got re tagged as homework by someone Say I am given the equation of position in one dimensional kinematics. Say its ...
1
vote
0answers
41 views

How much (little) wind force does it take to move a toddler in a stroller? [closed]

This question is raised because of the recent incident in a London subway station involving a stroller falling onto the tracks. The stroller was probably 10 feet (or 3 m) from the edge of the ...
1
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0answers
385 views

What is the angle of projection when at maximum height the speed of a projectile is half the speed at half the maximum height? [closed]

I have been struggling with this problem: The speed of a projectile when it reaches its maximum height is one half of its speed when it is at half its maximum height. What is the initial ...
0
votes
1answer
91 views

Why is the range for a particle thrown at 90 degree same as that of a particle thrown at 0 degree?

There is a derivation given in my book which concludes to the fact that the range is same for two angles of projection, provided they are complementary. I fail to understand this fact. For example, ...
1
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1answer
207 views

Will A Vertical Projectile Travel the Same Distance as A Horizontal Projectile

If a projectile is fired vertically from an initial height, $h$, above ground level, and an identical projectile is fired with equal initial velocity from the same initial height in the horizontal ...
1
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2answers
181 views

What is the relative acceleration of a projectile fired at in a low gravity vacuum?

This question is to end an old argument. Given a (space) vehicle with an acceleration of X, and projectile with an acceleration of 2X (rocket, not bullet), what would the relative acceleration of the ...
2
votes
1answer
125 views

Distance along projectile motion [closed]

I was doing kinematics these days, projectile motion. And I did the basic concepts: range, max height, time of flight, projectile on inclined plane. I am curious to know how we would solve a question ...
3
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3answers
81 views

The motion of the particle satisfies $\textbf{v} = \textbf{c}\times \textbf{r}$

Why does a particle with position $\textbf r(t)$ that satisfies $\textbf{v}(t) = \textbf{c}\times \textbf{r}(t)$ follow a circle that lies in a plane perpendicular to $\textbf{c}$ with centre on a ...
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2answers
366 views

Kinematics problem involving rocket

A rocket is fired vertically and ascends with a constant vertical acceleration of 20 m/s^2 for 1 minute. It's fuel is then all used and it continues as a free particle. Find the Maximum height ...
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3answers
151 views

How to approximate acceleration from a trajectory's coordinates?

If I only know $x$- and $y$- coordinates of every point on a trajectory without knowledge of time information, is there any way to approximate Cartesian acceleration angle at each point? Time interval ...
1
vote
1answer
200 views

Average Velocity of a body moving in a circle with constant speed $v$ [closed]

A Body is moving with constant speed $v$ along a circle of radius $R$. Find the average velocity of the body from time $t = 0 $ to $t= \frac{R}{3V}$. My attempt at the question: Let distance ...
0
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2answers
534 views

Find the max projection angle so that distance from point of projection always increases

We want to launch a projectile from the surface of earth so that its distance from the point of projection is always increasing. What is the maximum angle of projection for which this is possible? ...
1
vote
2answers
70 views

Kinetic Energy of a Particle [closed]

Consider a particle of mass $m$ in $6$ dimension. Its coordinate w.r.t. origin $\left(0,0,0,0,0,0\right)$ is given as $\left(x,y,z,\dot{x},\dot{y},\dot{z}\right)$. If we denote $r = ...
1
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1answer
1k views

What is the difference between negative acceleration and decreasing acceleration?

According to Reisnick and Halliday, retardation is the acceleration in the negative direction of time axis ie. opposite to the motion. Decreasing accleretion is the decrease in the magnitude of time ...
2
votes
1answer
135 views

How to measure trajectory regularity? [closed]

I have two animal running trajectories. A regular one with repeated back and forth running between point A and B, like the one on top in the figure. The other one is very irregular, animal paused and ...
0
votes
1answer
82 views

Calculating force of a car [closed]

I'm simulating car cruise system and my results are not making any sense. I have been told that my force formula is wrong but I don’t understand why it is wrong and how I can fix this. Does anybody ...
0
votes
1answer
48 views

Interaction of solid objects and change of trajectory

I have two solid objects. Each of them has an arbitary complex surface, which is discribed by set of vertices. The aim is to describe their interaction, result of which is the change in trajectory of ...
1
vote
1answer
77 views

Distance and velocity question

I know that speed is the derivative of distance. So integrating speed should give you distance. Let's suppose we have a speed which obeys this function: $$ v(x) = 2^{2^x} $$ So at time 0 the speed ...
2
votes
2answers
160 views

What is the difference between 'flow' and 'move'?

I just met with a very basic question.(Might even sound silly!) My textbook kinda says(not exactly), 'Whatever flows is a fluid'. That got me wondering because we are creating a whole category of ...
0
votes
1answer
37 views

Area covered by particle between it's path and horizontal lines

Question: The maximum range of projectile is $R$ and the maximum height attained by the particle is H. If the area covered by the particle between its path and horizontal line is $A$, then ...
0
votes
2answers
322 views

Time of flight for a projectile with stated initial velocity and size at various distances

I've been mooching round the internet looking for an answer to this one and can't find a ready resource, hence the question. In short, I'm trying to discover the flight time of a shotgun pellet at ...
-1
votes
2answers
220 views

What strategy should I use to approach this problem? If my straight line approximation doesn't work [closed]

recently i wrote an assignment in one of the questions i got two different answers for the same question by considering a straight line motion The question was somewhat like this THIS IS A HOMEWORK ...
-1
votes
1answer
145 views

How to derive this formula? [closed]

as far as i know the range of an obliquely projected body which is projected with a velocity of u with some angle $\theta$ with the horizontal under the action of gravity is R=$u^2sin2\theta$/g by ...
1
vote
1answer
362 views

The dimensional formula of distance travelled in $n$th second

I read that the dimensional formula of distance traveled in $n^{th}$ second is same as that of velocity. Okay, the formula for the distance traveled in $n^{th}$ second is $s_t= u+\frac{a}{2}(2t-1)$ ...
4
votes
3answers
1k views

Why does light travel at the same speed when measured by a moving observer? [duplicate]

I know the hypothesis that the light speed is constant is retained by experiments. But is there any theory explaining why the light speed is constant no matter how an observer moves relative to light? ...
0
votes
1answer
62 views

Elementary question about velocity

When we talk about the nonvanishing velocity of an object, are we assuming we are static relative to the object or not?
-1
votes
3answers
338 views

Projectile Motion with air Resistance - Adjust only the Angle to hit a target

OK, let me preface this by saying i am not a physics student, nor have i ever been. I am a software engineer working on a development degree. So this is homework but the assignment was just to create ...
1
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3answers
749 views

Is there a difference between “average acceleration” and centripetal acceleration?

Question adapted from Examkrackers MCAT prep book: A particle moves along a half circle (diameter=$10\text{ m}$) at a constant speed of $1\text{ m/s}$. What is the average acceleration of the ...
2
votes
4answers
705 views

How to calculate a collision which is partly elastic and partly inelastic?

(For the purpose of this question, "calculating a collision" means: given the velocities and masses of two objects in a collision, figuring out the new velocities of both objects after the collision). ...
6
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5answers
4k views

Can an object reverse its direction of acceleration even though it continues to move in the same direction?

Can anyone please explain me on this matter along with day to day examples?
5
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3answers
2k views

Ball thrown from a moving train

This is not a question about throwing a ball vertically in a moving train. I am asking what would happen if I throw a ball in a horizontally in a moving train. Assume I am facing an exit door of a ...