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)

0
votes
1answer
8 views

Initial Velocity Question

What is the initial velocity vertically when a person jumps 0.5 metres into the air, neglecting horizontal movement. Is it just 0 m/s? And the final velocity would be -9.8m/s^2 * the time it took took ...
0
votes
0answers
8 views

Motion in a Plane Velocity

If I were to throw a rock of a cliff at 12 m/s as a horizontal velocity, what will the final velocity of the rock become when it hits the ground? I am tempted to say 12 m/s because the horizontal ...
-1
votes
0answers
6 views

Motion in a Plane Question [on hold]

I don't understand how to do this problem: You are the pilot of a small plane and want to reach an airport, 600km due south, in 4.0h. A wind is blowing at 50km/h[S35oE]. With what heading and ...
-1
votes
0answers
19 views

Vertical Motion Question [on hold]

Question: An object is projected vertically to to the ground in a 20 m/s velocity. After 3 seconds another object is projected from the same position in the same velocity to the same direction. ...
0
votes
0answers
18 views

Analysing kinetic energy in different frames [duplicate]

Case A: Say we observe a body X moving with a velocity of 30 on the +x and we(the observer) are stationary. Case B: The observer moves with a velocity of 50 on the -x. The body X is moving in the ...
-1
votes
0answers
22 views

Pls help me visualise this situation, I'm not able to understand it [on hold]

Find time of flight of projectile thrown horizontally with speed 50m/s from a long inclined plane which makes an angle theta= 45° from horizontal.
-3
votes
0answers
38 views

Movement of a box containig a particle [on hold]

A small thought experiment: Imagine a rectangular box in space, containing particle, all resting at $t=0$ from your point of view. At some point in time $t>0$ the particle starts to move with ...
-1
votes
0answers
21 views

Projectile motion and bouncing [on hold]

Prove that the number of bounces n after throwing an elastic ball on a frictionless surface with a known angle (j)relative to the horizon and the angle of the initial velocity is known also (k)..is ...
-4
votes
1answer
28 views

projectile on an inclined plane [on hold]

Is the time of ascent equal to the time of descent? I tried it but I am not being able to prove it mathematically.
1
vote
1answer
39 views

I don't understand the approach used in solving this kinematics problem

The problem text is as follows: During the first half of a straight path, which is at $\alpha_1=60°$ relative to a reference line, a car is travelling at $v_1=72 km/h$. During the second half of the ...
10
votes
4answers
180 views

Problems in the relation $a=v\frac{\mathrm{d}v}{\mathrm{d}x}$

We all know $a = \frac{\mathrm{d}v}{\mathrm{d}t}$. A little application of the chain rule leads to the relation $$a=v\frac{\mathrm{d}v}{\mathrm{d}x}$$ But the above equation shows that $a=0$ whenever $...
-4
votes
1answer
45 views

Differential velocity and acceleration [on hold]

A particle moves along the curve $X = 2\sin3t$, $Y = 2\cos 3t$, $Z= 8t$ How to find the velocity and acceleration when $t>0$?
8
votes
1answer
79 views

Can one rise through a free-falling rope?

I am a little confused about this question. I cannot imagine that it is possible to rise through a rope (assuming inextensible) that isn't fixed in its upper end. But when I solve this problem, I see ...
0
votes
3answers
43 views

Why is the sign of the tangential component of acceleration negative in this problem? [closed]

Since the train is slowing down at a constant velocity, shouldn't the acceleration equal zero? Why is it negative in this case?
-1
votes
3answers
727 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
votes
1answer
115 views

Difference between classic velocity and spatial velocity [closed]

I am reading a tutorial about a physics simulator I am using, and it has the following code (in C++, but not important): ...
-4
votes
0answers
23 views

Pls solve this question of projectile motion [closed]

2 particles are projected one by one with same initial velocity from the same point on the ground, they follow same parabolic trajectory and are found to be in same horizontal level, separated by a ...
3
votes
4answers
122 views

Intuitive explanation of the half in the $\frac{1}{2}at^2$ distance equation?

The full equation $$ Xf = X_o + V_o t + \frac{at^2}{2} $$ is integrated from the velocity function (which was integrated from constant acceleration function), right? The problem is, I can't seem to ...
8
votes
1answer
378 views

Is it possible to determine particles' velocities from their crossings on a ring?

2 particles are constrained to move in a ring. Both particles begin moving at $t=0$ from $p=0$, each particle moving in the opposite direction of the other. It is known that they are moving at ...
2
votes
1answer
196 views

In perfect vacuum (no external force), if I apply a small amount of force to a body, will it continue to accelerate forever?

According to the equation $F = ma$, the greater the force applied to a body, the greater its acceleration. But in a place where there is no gravity or any other kind of external force, if I apply a ...
1
vote
3answers
513 views

Projectile, air resistance and wind

So for my school project I am working on a projectile simulator and air resistance. So I have looked at this. Equations for an object moving linearly but with air resistance taken into account? ...
5
votes
3answers
198 views

Does $y$-motion really have nothing to do with $x$-motion?

I am watching a Physics 1 for physical science majors on coursera.com, and in one of the concept tests there is a question that goes like this; "A bullet is fired horizontally from a rifle on the Moon ...
0
votes
3answers
1k views

In a 2D problem with a thrown object, why is the acceleration along the x-axis equal to 0?

I'm starting Physics, and I don't understand why the acceleration along the x-axis is zero for an object thrown near the surface of the Earth. This may be problem specific, but I wouldn't know since I ...
0
votes
1answer
43 views

Equation confusion regarding finding acceleration [closed]

Physics newbie here, sorry if this is super basic... I am learning about kinematic equations and am having difficulty reconciling two of the equations. Let's say I begin driving and after 1 second ...
2
votes
2answers
75 views

Circular Motion. Intuition on vectors as a physics interpretation [closed]

I am a maths undergraduate. I decided to start studying some basic physics trying to be rigorous with the math and uderstand the interpretations of some of the mathematical constructs and see how ...
1
vote
2answers
54 views

If change in position over time is average velocity, why doesn't change in position over time squared equal average acceleration?

For example, let's say a car is experiencing an acceleration of $1$m/s$^2$, for $6$ seconds so it goes $18$m. Now the average velocity is found through dividing $18$m by $6$s which is in line with the ...
0
votes
3answers
541 views

Horizontal and vertical acceleration of a ball on a slope?

I understand that you resolve the components of the balls weight parallel and perpendicular to the slope in order to calculate the force due to gravity that actually acts down the slope. The ...
-1
votes
1answer
24 views

How to estimate the relative motion using kinematic equations?

Background I am reading the following thesis: Todosiev, E.P., 1963. The action point model of the driver-vehicle system. On page 9 it describes the relative motion between 2 cars as follows:...
0
votes
1answer
310 views

Kinematics of a differential drive robot

(I am reposting here a question I asked on stack overflow, since it actually sits right in between programming (modeling of 2D physics) and physics proper (kinematics). I think I have the physics part ...
1
vote
2answers
388 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 Newton's third law and momentum conservation. Here is what I have tried. Lets take a ball mass of $m_1$ (index 1 is the ...
0
votes
0answers
31 views

Does this calculation give displacement or distance?

So we have velocity as a function of time given $\overrightarrow{v}(t)=(1-2bt)k\overrightarrow{r_0}$ where $b,k$ are positive constants and $\overrightarrow{r_0}$ is a unit vector. It is found that if ...
0
votes
1answer
189 views

Newtons 3rd law, on two opposing discs?

Assume we have a large disc at rest (bottom disc), which is free to move. Above it there is another disc (disc2) that's rotating, and a motor fixed on that large disc (bottom disc) as well, that load ...
0
votes
2answers
205 views

Kinematics equations of motion find x position in 2D from height

I have a question and I thought of 2 possible ways to answer it however the resulting answers are different which means I must be doing something wrong in my calculations. All the below happens 2 ...
7
votes
2answers
2k views

Should acceleration be included in state vector of a Kalman filter?

I'm developing (actually adopting existing solution) a Kalman filter to model motion of a vehicle (UAV or automobile). The state vector will include position, velocity, and, possibly, acceleration. ...
1
vote
2answers
36 views

Is the magnitude and direction of gravity on an object the same as the objects vertical velocity?

I need to make a diagram for an entry level college physics class. I need to show the magnitude and direction of gravity on a flying object and also show the magnitude and direction of the objects ...
3
votes
2answers
380 views

Projectile motion maximum distance to origin

Is there an elegant or easy way to derive the maximum distance from the origin to a point of the parabola created by projectile motion (assume initial position is the origin)? Other than ...
6
votes
1answer
117 views

Why doesn't the relativistic formula for momentum appear consistent with collisions?

The relativistic formula for momentum is $$p = \frac{mv}{\sqrt{1 - \dfrac{v^2}{c^2}}} \,.$$ In the following example, I apply the formula in the most basic way possible to the addition of velocities. ...
0
votes
1answer
62 views

Position / velocity / acceleration vs time graphs when falling towards a black hole

In Newtonian physics, as far as I understand it, for a small object falling towards a massive object, the graphs of position, speed and acceleration vs time look like this: (If the massive object ...
0
votes
1answer
68 views

Projectile motion on an inclined plane [closed]

Two parallel straight lines are inclined to the horizontal at angle $\theta$. A particle is projected from a point midway between them so as to graze one of the lines and strikes the other at a right ...
1
vote
2answers
203 views

Computing Acceleration in mass and pulley system using conservation of energy

I have a question in which a multiple pulley and mass system is being analysed. I can compute accelerations and Tension without any issue using newtons second law. However I am asked to use ...
2
votes
2answers
264 views

Projectile motion - calculate landing angle

A projectile is launched at a $45^\circ$ angle, aiming for a target at a distance of 15 feet away from, and $2$ feet below the starting position. I'm looking for equations to determine: The ...
0
votes
1answer
250 views

Inclined plane, circular motion and the friction

Suppose we have a cylinder on an inclined plane of mass $m$ and radius $R$ moving without sliding (so that $\varepsilon = a/R$). Why is the friction $F$ causing the circular motion sometimes lower ...
0
votes
2answers
239 views

Find the force needed to accelerate body to a certain velocity for a certain time with respect to drag force

So, the problem is straightworward when we suggest that air resistance force is constant: $$ \vec F = \frac {\vec V_1 - \vec V_0} {t} m / b $$ $$ \vec V_0, \vec V_1 - \text {initial and final ...
2
votes
3answers
3k views

Speed of a fly inside a car

A couple of weeks ago I was travelling in a car (120 km/h approximately) and I saw a fly flying in front of me (inside the car, near my nose, windows closed). I wonder how was that possible. Does it ...
9
votes
1answer
1k views

Is running in a zigzag helpful in avoiding being shot by an arrow? [closed]

Two people A and B start at a certain point. B runs away from A to another point. A shoots arrows at B. Is it helpful for A to run in a zigzag rather than in a constant direction? To be more ...
-3
votes
0answers
33 views

Contradictory kinematics formula [duplicate]

The displacement of a particle in the $t$th second of its motion is given by: $$ S(t)=u + \frac{a}{2}\left(2t-1\right) $$ where $u$ is the initial velocity, $a$ is the acceleration and $s$ is the ...
1
vote
1answer
390 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 ...
5
votes
3answers
1k views

Has a body angular momentum and torque only in a circular path?

In different contexts, my book(Principles of Physics by Resnick, Halliday ,Walker) , they wrote For torque, the path need no longer be a circle and we must write the torque as a vector $\vec{\tau}...
0
votes
1answer
23 views

Find the initial velocity's angle of a projectile knowing only the ratio between the horizontal distance traveled and max height

The ratio between the horizontal distance traveled and the launch height is 3 to 1. I think it is possible to find the angle given this information, but how exactly do you do it? I think it's arctan(2/...
-1
votes
1answer
80 views

What happens if you fly a drone inside moving passenger airplane? [duplicate]

I have a little question. If I mark an X in the center of a passenger airplane, and try to fly a drone from the X mark in the moving passenger airplane (800-900 km/h), what will happen to the drone? ...