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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2
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3answers
203 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
votes
2answers
49 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? ...
1
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1answer
87 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. ...
1
vote
1answer
68 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
vote
1answer
110 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
83 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
45 views

Deviation from 2D trajectory

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
84 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
54 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
80 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
90 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
votes
1answer
72 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
43 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 ...
-3
votes
1answer
38 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
votes
2answers
92 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
202 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
25 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
vote
0answers
229 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
75 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
vote
1answer
96 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
140 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
77 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
votes
3answers
77 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 ...
1
vote
2answers
99 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 ...
1
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3answers
54 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
91 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
votes
2answers
235 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
61 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
vote
1answer
329 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
85 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
65 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
73 views

hydraulic scissor jack lifting capacity

Can you please assist with a really simple question? I have a hydraulic scissor jack table with the following: 2 hydraulic cylinders, each with a cylinder stroke of 240mm, a cylinder bore of 50mm ...
0
votes
1answer
45 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
70 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 ...
0
votes
1answer
30 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
138 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
207 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 ...
-2
votes
1answer
105 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
103 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
555 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
34 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?
-2
votes
3answers
239 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
vote
3answers
238 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
209 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
votes
5answers
3k 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
votes
3answers
1k 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 ...
1
vote
3answers
356 views

Calculate vertical distance using acceleration

I have the following scenario: an iPhone is connected to a vertical rail (it's motion is restricted to the Y axis). Through mechanical means the phone is forced upwards and then allowed to return to ...
-1
votes
1answer
28 views

What should be used, $v=r \omega$ or radial and transverse components? What would be the next step? [duplicate]

An aircraft A is flying in a vertical plane containing two tracking stations P and Q which are 15km apart. At a cetain instant θ (measured anticlockqise from horizontal line PQ to the line PA) is 60° ...
41
votes
5answers
13k views

How effective is speeding?

At a simple level, speeding in a car attempts to minimize the time required to travel a distance by utilizing the basic relationship: $$d=st$$ So for a given distance, time should be inversely ...
1
vote
1answer
68 views

i can't detect what wrong have i done in a kinematics problem [closed]

a question was given to us in assignment which was as follows A person moves 20 metres towards north then 30 metres towards east and then moves 30 x 1.414 metres towards south west. The whole ...