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.

learn more… | top users | synonyms (2)

1
vote
2answers
223 views

Computing distance traveled from jerk

When dealing with higher time derivatives like jerk, how does one find the distance traveled? Can it be calculated by just knowing time?
1
vote
2answers
235 views

Position dependent speed, how to compute position

I can't solve a problem: $ A= 0.5 (ms)^{-1}$, $ x_0 = 0.5 m $, $v(t)= A \cdot x^2 $, I have to compute the position at $t=3$ ($x_0$ is the initial position). So my guess is that I should be able ...
1
vote
1answer
99 views

Why does a difference in approach to projectile motion yields different results?

A body is projected vertically upwards from the surface of the earth with a velocity equal to half the escape velocity. If $R$ is the radius of the earth, then find the maximum height attained by the ...
1
vote
2answers
13k views

Preventing a block from sliding on a frictionless inclined plane

I want to demonstrate what force $F$ you would have to exert on an inclined plane of angle $t$, mass $M$ to prevent a block on top of it with mass $m$ from sliding up or down the ramp. I worked out ...
1
vote
3answers
722 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
vote
3answers
1k views

Overtaking with non-constant acceleration

I have tried to solve this problem by adding the sum of the displacements during acceleration, constant velocity and deceleration, but it does not work out. Question: A car accelerates from ...
1
vote
3answers
11k views

Stopping Distance (frictionless)

Assuming I have a body travelling in space at a rate of $1000~\text{m/s}$. Let's also assume my maximum deceleration speed is $10~\text{m/s}^2$. How can I calculate the minimum stopping distance of ...
1
vote
3answers
257 views

Does circular motion cause centripetal force OR does centripetal force cause circular motion?

Does circular motion cause centripetal force, or does centripetal force cause circular motion, or are they both occurring hand in hand together instantaneously? One more question: If I project a body ...
1
vote
2answers
224 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 ...
1
vote
1answer
280 views

If the velocity of particle $A$ exceeds that of $B$, is the acceleration of $A$ greater than $B$?

Two particles $A, B$ are travelling along parallel straight paths. At some point, the velocity of $A$ exceeds that of $B$. Does this necessarily mean that the acceleration of $A$ is greater than the ...
1
vote
1answer
2k views

Simple Projectile Motion Question

A volcano erupts 50m below the sea level. A rock leaves the crater at 20 m/s at an angle 30 deg with the vertical line. The rock has a mass of 15kg. IGNORE WATER RESISTANCE. It gets out of the water, ...
1
vote
2answers
70 views

Doubt on series springs [closed]

Here is a description of the motion of two springs in series. The premise is that the force on the two springs is the same. This is derived from the following reasoning: when I pull the mass with a ...
1
vote
2answers
52 views

May a point rotate about itself?

Suppose we have two equivalent rigid cylinders. Cylinder 1 is moving (translating) with constant velocity of v. Cylinder 2 is rotating without slipping and its center’s velocity is constant and equal ...
1
vote
3answers
45 views

Why the similarity in the Equations of Motion for Rotational and Rectilinear Motion?

These are the equations of motion given constant acceleration, for first rectilinear and then rotational motion. Rectilinear Motion: Rotational Motion: While the variables have changed, and the ...
1
vote
3answers
458 views

Can the force acting on a body remain constant if the body is accelerating?

Since $F=ma$, the force should change if acceleration changes shouldn't it? And since acceleration is the rate of change of velocity, can velocity be constant if acceleration changes?
1
vote
1answer
633 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 ...
1
vote
3answers
273 views

Uniform Circular Motion and Centripetal Acceleration

In introductory physics books (or at least mine) it limits the equation $a_c=v^2/r$ to the situation where the speed around the circular path is constant. It enforces the idea that the speed is ...
1
vote
2answers
566 views

Help with a solid sphere sliding and then rolling

Initially at time $t=0$, a solid sphere slides with velocity $v$ along a horizontal surface. The coefficient of friction is u. Find the required time for the sphere to stop sliding (the sphere will ...
1
vote
4answers
2k views

When we take time derivative of a function of time, then is the result another function of time, again?

(I'll try to explain my question by one known example), for example where the velocity is a function of time v(t) then its time derivative (which is acceleration: $a=\frac {dv}{dt}$) is another ...
1
vote
3answers
174 views

Doubt in Kinematics

I know that this isn't the place for such basic questions, but I didn't find the answer to this anywhere else. It's pretty simple: some particle moves in straight line under constant acceleration from ...
1
vote
2answers
211 views

Non-zero higher time derivatives of position?

My mom told me to use speed control, which would allow the car to remain at constant speed. I told her that its impossible for a car to maintain constant speed, as slight changes in friction on the ...
1
vote
3answers
8k views

Calculating car's acceleration from change in angle of hanging object?

The question essentially is based on a situation like this- A car has a small object hung from the cieling on a string (apparently at an angle of 0 degrees to the ceiling). The car is accelerating ...
1
vote
3answers
3k views

Uniform Circular Motion

Why does the object not go inward, into the circle if the acceleration is inward? I think its because the velocity to outward? So they sort of cancel each other out? But if the speed is kept ...
1
vote
2answers
246 views

Should the cold drink come out of a free falling bottle with an open lid?

If I hold an open bottle and perform free fall, say sky diving, along with it from, say 10000ft, while I'm holding the bottle vertically upwards should the cold drink come out of the bottle? Kindly ...
1
vote
3answers
195 views

If my acceleration is -1 ($a=-1\:\rm{m/s^2}$) and I'm standing in the infinite ($x_0=\infty \:\rm m$), could I reach the point $x=0\:\rm m$?

I'm standing in the infinite where $x_0=\infty \:\rm m$. If I have a negative acceleration, could I reach the point $x=0\:\rm m$? Would it be possible to calculate how long would take to reach the ...
1
vote
2answers
3k views

Sign of Velocity for a Falling Object

I'm working on a homework problem in Mathematica. We have to graph the height and the velocity of a function given an initial height and initial velocity. However, when I do the graph for the velocity ...
1
vote
2answers
11k views

How to prove that a motion is Simple Harmonic Motion (SHM)?

I would like to know how one could show and prove that a given motion is simple harmonic motion. Once given an answer, I'll apply that technique to an example I am trying to figure out. Thank you ...
1
vote
2answers
512 views

Using acceleration to plot position

Sorry if this question is dumb, and I know is physics 101, but I'm not that good with physics. I'm writing an iPhone program that by collecting the acceleration data of the device tries to replicate ...
1
vote
4answers
2k views

Would you feel weightless if falling or flying up in a vacuum?

Ignoring that you can't survive in a vacuum. If you were to jump of a ledge in a vacuum (in a vertical tube eg). While falling would you feel weightless? Surely the earths gravity is still pulling ...
1
vote
2answers
76 views

The force causing galaxies to accelerate away from each other?

The galaxies in the universe appear to be accelerating away from each other according to the Doppler shift that is present in the light we receive from other galaxies. According to Newtonian ...
1
vote
2answers
56 views

accelerating and non accelerating duality of matter

Kinetic energy of any object , assumes accelerating nature of the object as it is derived from equations of motion for uniformly accelerated objects and the work-energy theorem which deals with ...
1
vote
1answer
55 views

Given a current velocity and a fixed input energy, how much faster will a relativistic particle be?

The relativistic kinetic energy of a particle with mass $m$ and velocity $v_0$ is $$m c^2 (\gamma_0 - 1) \textrm{ where } \gamma_0 = \frac{1}{\sqrt{1 - \frac{v_0^2}{c^2}}}$$ I would like to know how ...
1
vote
3answers
74 views

Initial speed in homework problem [closed]

This is a homework question. I tried to solve it, but failed. I had to translate this question, so please forgive me if it is poorly worded. In this question you can ignore the atmospheric ...
1
vote
1answer
42 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\, ...
1
vote
2answers
247 views

Question about kinetic energy

I have a question about kinetic energy: Imagine two vehicles with velocities $v_1$ going at $30 \frac{\text{m}}{\text{s}}$ and $v_2$ at $50\frac{\text{m}}{\text{s}}$. If they hit each other, will ...
1
vote
1answer
100 views

How to explain this to my sir

We all know that $f = ma$. But for finding displacement, we always use: $$ s = s_0 + ut + \tfrac{1}{2} a t^2 $$ My sir, i don't know why for some reason uses this weird method: $$ F = ...
1
vote
2answers
283 views

At what point does force stop translating an object and start purely rotating it? [duplicate]

At what point (or distance) from the axis of rotation, does force applied on a rigid body stop translating and purely rotating the body? Can such a point even exist? Does the body always have to ...
1
vote
2answers
2k views

Why does a plane look like it's slower than a car?

Recently, I was in a car and noticed a plane in the sky. What was interesting was that the plane seemed to go slower than my car because I passed the plane. Is there a physics reason to this?
1
vote
1answer
106 views

Are velocity and acceleration smooth quantities?

My thinking: acceleration corresponds to a force which is instantaneous, so the acceleration of a rigid body can be rather spiky (non-smooth) velocity (angular velocity) describes the ratio of ...
1
vote
1answer
2k views

What are the equations for motion with constant jerk?

Every one knows the three famous equations for motions with constant acceleration . But what if the motion were having a jerk? How should then be the equations for motions? How can I find them?
1
vote
2answers
263 views

Quick question on free fall of 2 objects [closed]

I am trying to work through a problem, that is basically telling me that two objects were dropped from a building, one was thrown 2 seconds after the previous object, and I have to find out how long ...
1
vote
3answers
358 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 ...
1
vote
2answers
752 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 $s_t= u+\frac{a}{2}(2t-1)$ ...
1
vote
1answer
77 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 ...
1
vote
2answers
1k views

Increase in velocity by loss of mass? [closed]

A trolley of mass 300kg carrying a sand bag of 25kg is moving uniformly with speed of 27km/h on a frictionless track. After a while, sand starts leaking out of a hole on the floor of the trolley at ...
1
vote
2answers
512 views

Measuring the velocity of a pendulum using the width of the bob

I did an experiment on pendulum motion and in the method it says use the following equation to measure the velocity of the pendulum: $$v=\frac{W}{t}$$ where $W$ is the width of the pendulum bob and t ...
1
vote
3answers
754 views

How does this chair move?

I have a chair like this(shown in figure). I was kneeling on the part where we sit. I just gave a sudden push to the part where we rest the back, without moving my legs. I found that the chair is ...
1
vote
3answers
1k views

Calculate kinematics of body movement from the set of spatial coordinates

Short intro I have a set of 3D (x,y,z) spatial coordinates of arm movement obtained using motion capture system. The example set of such coordinates looks like this (rounded up): ...
1
vote
1answer
254 views

why does perpendicular motion to the direction of someone' s approach does not affect the distance between them

I was reading about the the four turtles/bugs math puzzle Four bugs are at the four corners of a square of side length D. They start walking at constant speed in an anticlockwise direction at all ...
1
vote
2answers
928 views

Motion of a rod struck at one end

Imagine a strong metal rod of uniform density and thickness floating in a weightless environment. Imagine it lies on an X-Y plane, with one end (A) lying at 0,0, and the other end (B) at 0,1. Then it ...