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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-3
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3answers
44 views

Average speed without given distance [on hold]

Here is the problem where the speed is given but not the distance and need to find the average speed.
2
votes
2answers
254 views

How to find Tangential/Radial/Angular Velocity for motion in any curve?

Is the radial velocity responsible only for changing distance between objects and the component perpendicular to it only for change in direction? If so why? Please try to give a different explanation ...
1
vote
1answer
108 views

Deriving the equation of motion for a rigid system

I want to derive equation of motion for the system shown in picture. How do I choose a generalized coordinate in order to calculate kinetic and potential energy of the system? I need the ...
-2
votes
3answers
54 views

What is acceleration of A and how to approach such accelerating pulley problem [on hold]

As shown in figure A and B are free to move pulley and rope are mass less, there is no friction at all between any two. Now my question is because of tension in rope, A will move left but how will B ...
8
votes
1answer
751 views

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

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
1answer
187 views

General motion of a cone on an inclined surface

Suppose that a solid cone is placed horizontally on an inclined surface and is initially at rest. How will the cone move when it starts motion due to its weight? I know that its motion depends on the ...
0
votes
2answers
47 views

Projectile motion from platforms of different height [on hold]

So, I was thinking about the projectile motion example of an object launched from a Platform to the ground, and I started to wonder how you could calculate the example if the object was launched from ...
1
vote
1answer
42 views

Projectile question doubt [on hold]

A hunter wants to shoot a monkey with an arrow by launching the arrow at a speed $v_0$ at a distance of $L$ from the base of a tree of height $H$ on which the monkey is sitting. Now on watching the ...
0
votes
2answers
46 views

Simple change in velocity question

The hand of a clock is 1cm long. find the change in velocity of the hand in 15 seconds. The question is pretty simple, $v=2\pi R/T$ and then using the vector addition one can easily get answer which ...
3
votes
0answers
50 views

Branching ratio for a bound state

Consider the meson $\Upsilon(10860)$. It decays into $B\bar{B}$, $B\bar{B}^*+cc$ and $B^*\bar{B}^*$. The mass of $B$ is $5.28 ~\textrm{ GeV}$ and mass of $B^*$ is $5.33~\textrm{ GeV}$. The branching ...
8
votes
3answers
17k views
-5
votes
0answers
27 views

A car is moving with constant acceleration at 2 m/s/s. what distance will it have travelled when its velocity is 8m/s [on hold]

a car of length 3m is moving with constant acceleration at 2 m/s/s. How far will its front end be from the start point when its velocity reaches 8m/s The cars back end is on the start point and its ...
-3
votes
0answers
41 views

Kinetic energy of a suspended mass from an overhead crane [on hold]

I am using Lagrange's method to formulate the equation of motion for a 3D overhead crane that is shown below: For the formulation of the kinetic energy for the payload (suspended) mass. I have seen ...
0
votes
2answers
74 views

Solar Sail Questions

I'm just looking for a good (better) analogy. How do massless photons put pressure on a surface especially when it's a mirror? Using the analogy of the wind (atmosphere) on a sail breaks down when I ...
1
vote
2answers
40 views

Point object, Kinematics

I am very new to physics. This evening, I was reading about the concept of objects to be considered as point objects under some circumstances. And I was trying to think of circumstances under which ...
-8
votes
0answers
39 views

HELP WITH PHYSICS NUMERICALS? [closed]

Okay so ive a test tomorrow and i cannot get my head around these questions. Any help? :D A starts travelling from London to Paris at 8AM at 60mph. B starts following Aat 11am and catches A in 4 ...
0
votes
1answer
70 views

How do you arrive at this equation? $ \bar{v} = v_2 - \tfrac{1}{2} a \Delta t $

$$ \bar{v} = v_2 - \tfrac{1}{2} a \Delta t $$ $\bar{v}$ being average velocity and $v_2$ instantaneous velocity at one point this equation was used to find instantaneous velocity from average ...
0
votes
1answer
43 views

A projectile is thrown at angle θ with an inclined plane of inclination 45o . Find θ if projectile strikes the inclined the plane horizontal [closed]

My attempt: Vx=ucosθ - gsint(45)t Vy=usinθ - gcos(45)t These are the velocities after time t. Vx=Velocity along the plane after time t. Vy=Velocity perpendicular to plane after time t. As at the ...
2
votes
2answers
53 views

How can I find the maximum height if I have changing acceleration?

I'd like to find the maximum height that a projectile reaches in motion if I have a non-constant acceleration. How would I do this? What variables do I need to know in order to calculate this? ...
2
votes
1answer
112 views

How to calculate impulse force of body hitting water?

I'm calculating the force of a body hitting water from a high height. So far I've figured out the velocity at the time of collisions would be 40 m/s. The body is 78 kg. I seem to need the time it ...
-1
votes
0answers
28 views

Acceleration question- student running after bus [closed]

A student is standing 50 m behind a bus. As soon as the bus begins its motion with acceleration 1 ms-2, the student starts running towards the bus wit a constant velocity u. Assuming the motion to be ...
-1
votes
1answer
52 views

Rain and Man Problem [closed]

Rain is falling vertically with a velocity 2m/s. A boy at rest starts his motion with a constant acceleration of 2m/s^2 along a straight road. If the rate at which angle of axis of the umbrella with ...
5
votes
3answers
390 views

Extra vibrational mode in linear molecule

When calculating the number of vibrational modes for a molecule, the formulas differ for linear $(n = 3N - 5)$ and non-linear $(n = 3N - 6)$ molecules, where $n$ is number of modes and $N$ is number ...
-3
votes
0answers
57 views

Finding trajectory of a moving particle [closed]

At time t = 0 three particles ( A, B, C ) are situated at the vertices of an equilateral triangle $\Delta ABC$ of side length $d$. Each of the particles move with a constant speed $v$. $A$ always has ...
-1
votes
0answers
16 views

dc motor rotational kinetic energy [closed]

Rotational Kinetc Energy of an armature in left DC motor is given as: $\frac12n^2J_m(\dot\theta_l-\dot\psi)^2$ where n = Gear ratio $J_m$ = DC motor inertia moment $\theta_l$ = left wheel angle $\psi$ ...
8
votes
1answer
375 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
170 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 ...
0
votes
1answer
212 views

Explanation about friction force directions of two moving bodies in contact

can someone explain me why in this scenario (picture below) we have a friction force Ftr12 in the same direction as movement (left part of the picture, case 1 ) and how these directions of friction ...
1
vote
3answers
493 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? ...
-1
votes
2answers
38 views

Acceleration velocity relation

I just happened to come across this specific question in physics:- Q: If a particle is moving along a straight line with increasing speed, then, (1) its acceleration is negative (2) its ...
0
votes
1answer
49 views

Why does $k^z/E$ have dimensions of inverse velocity rather than velocity?

I'm studying quantum field theory and I want to prove the cross section. In Peskin's book, equation 4.77 says that: $$ \frac{1}{\left | \frac{k_{A}^{z}}{E_{A}}-\frac{k_{B}^{z}}{E_{B}}\right |}=\frac{...
1
vote
2answers
111 views

Intercept of 2 moving objects at constant acceleration

I have to make a simulation in which a guided missile has to hit an incoming enemy missile.The enemy missile "T" is the one which has to be intercepted and is only affected by gravity, the guided ...
0
votes
1answer
31 views

Area under the displacement-time graph giving time?

This is probably very stupid, but today at a lecture, our professor solved a problem where we had to find the time taken to travel from 0-5m, where $v = 3/x$ (velocity is a function of position.) ...
15
votes
3answers
878 views

Why there is a $\frac{1}{2}$ in the distance formula $d=\frac{1}{2}at^2$?

I'm preparing for my exam, but I have difficulties in perceiving why there is a $\frac{1}{2}$ in the distance formula $d=\frac{1}{2}at^2$?
-2
votes
1answer
26 views

Velocity ; Acceleration [closed]

A ball was thrown vertically upwards with a speed of 3m/s. The ball reached a highest point before falling down to the ground. What is the acceleration of the ball at the highest point? A 0m/s2 B ...
0
votes
4answers
86 views

Explain $\Delta x = v_0t + \tfrac{1}{2}gt^2$ please? [duplicate]

$g = \Delta v/t$, so $\Delta v = gt$. $v = v_0 + \Delta v$, so $v = v_0 + gt$. So if $\Delta x = vt$, then $\Delta x$ should be $v_0t + gt$. Why the $\tfrac{1}{2}gt^2$? I'm really confused, so this ...
0
votes
1answer
30 views

Acceleration at rest when ball is thown [duplicate]

If a ball is thrown vertically upward and it comes to rest for a moment, then its velocity decreases and becomes zero. Does its acceleration also becomes zero? If yes then how ball falls down?
2
votes
1answer
164 views

The norm of the vector sum of two 4-momentum vectors before and after pair production

Two photons traveling along the x-axis (in a lab frame of reference) of different frequencies are about to collide. Their 4-momentum vectors are (h$\nu_1$/c , h$\nu_1$/c , 0, 0) and (h$\nu_2$/c , -h$\...
1
vote
2answers
50 views

Can a system's internal forces change the system's motion?

Let say the motor makes the two rigid body rotate as a same velocity. (they rotate the opposite direction) then the Net force of the motor is 2Fsin(Theta). The acceleration of the motor is 2Fsin(theta)...
1
vote
4answers
49 views

Area under and slope of the motion graphs

I wanted to ask in general what area under the graph means. Also which physical quantity is highlighted by area under distance vs time graph. I'm confused that area is a 2 dimensional concept and it ...
-1
votes
3answers
56 views

How to solve this one dimensional motion question? [closed]

I was able to deduce the following information from the problem: acceleration of police = 2m/s^2 x0 = 50 meters t= 5 seconds final velocity = 0 m/s However, I'm not sure what to do next.
1
vote
2answers
54 views

Finding if two objects collide

The question that I'm trying to understand is this: This is the part of the solution I don't understand: From my knowledge, if $v_p-v_q$ is due south, this means $r_p-r_q$ is also due south, ...
0
votes
0answers
56 views

Physical pendulum dynamics confusion

I'm validating a Matlab Simulink SimMechanics model analytically. The model consists of a physical pendulum (uniform rod with length $l$ and width $w$) which is torque driven. I'm somewhat confused ...
1
vote
2answers
434 views

Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...