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# Questions tagged [kinematics]

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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27 views

### Icas year 6 question 2010 [closed]

Can you please assist me with the question below? Trying to explain it to my teenager.
1 vote
36 views

### Defining Free Fall: Does Gravity Need to be the Sole Force Present?

Can a scenario be considered free fall in physics if the work done by forces other than gravity is zero, but those forces are still present? Or is it necessary for gravity to be the only force present ...
24 views

### Orbital motion described from an external frame of reference

I am working on proyect where I have to simulate a rocket mission to Mars, and I am having some trouble with it so I wanted to check if my math is ok. The frame of reference I am using to describe the ...
44 views

### Kinematics-Acceleration [closed]

I know uniform acceleration is, When an object is moving with an increase in velocity at equal intervals of time, then the object is said to be in uniform acceleration. my text book shows all kinds of ...
30 views

### A projectile is launched from point A with the initial conditions shown in the figure. BC part is circular with radius 150m [closed]

I have tried two approaches for this question. First, I tried finding out the vertical angle from the radius but I couldn't do that. Then I tried the second approach, by equating the equation of ...
43 views

### Why is initial velocity 0 for retarding motion? [closed]

Issue details Why retarding has initial velocity 0? It should be same as max speed of the previous motion of the body. if you kindly look at this question: https://byjus.com/question-answer/a-car-...
20 views

### Projection on inclined plane- comment about magnitude of position vector [closed]

A projectile strikes the inclined plane perpendicularly as shown. Is the statement below correct : Magnitude of position vector joining O to the projectile never decreases Intuitively it feels like ...
52 views

### What do we get on differentiating the instantaneous displacement function?

I was doing kinematics when a silly question came to my mind. It is as follows: When we differentiate $x(t)$ (position as a function of time), we get $v(t)$ (instantaneous velocity). Doing the reverse,...
21 views

### Which energy and forces need to be considered in a looping problem with and without a supporting rail system? [closed]

I have an assignment in physics and I can't understand the difference between the 2 questions. That's the question A skier with mass $m = 70$ kg stands on a ramp of height $h$. At the foot of the ...
11 views

### Velocity-displacement graph for a motion with uniform retardation then uniform acceleration [closed]

What will be the v-s graph of a body in vertical motion (neglecting the air resistance) as it first experiences a retardation of g $\mathit {m/s^2}$ and then an acceleration of g $\mathit {m/s^2}$?
906 views

### Mass travelling with constant speed in a circle

Imagine a 2D circle has a point mass traveling along its circumference with constant speed. The only force experienced is centripetal. However, if we take the 2D plane the circle sits on and rotate it ...
26 views

### Rate of change of distance between two bodies with like charges [closed]

Two small balls having the same mass and charge are located at the same vertical at height $h_1$ and $h_2$ are thrown in the same direction along horizontal at velocity v. The 1st ball touches the ...
1 vote
49 views

### Shooting a bullet in motion

If a bullet is shot from a firearm from a moving car in the direction of movement, would the speed gained with respect to the car be same as the speed of a bullet that is shot from an immobile gun? I’...
56 views

### Chain rule when the intermediary variable might be equal to zero

I came across the following question in the kinematics section of my introductory physics textbook: The velocity of a particle moving along x-axis is given as $v=x^2-5x+4$ (in $m/s$), where $x$ ...
46 views

### For an object in motion if $u=\hat i + \hat j$ and acceleration $a= \hat i + \hat j$ how will its parametric graph look like look like in $xy$-plane? [closed]

I believe graph would be a straight line at 45 degrees from x axis and that would represent a 2D motion but one of my teachers said that if graph is a straight line then it is one dimensional motion. ...
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### I need to gain an understanding of the normal reaction, specifically on a circular motion

To my understanding, normal reaction is a force that pushes in the opposite direction of gravity, in order to keep the object from falling, or phasing through the surface. Though, what happens when we ...
1 vote
57 views

### Acceleration $v = sin (100t^2+2)$.? [closed]

The relationship between the velocity of the top of a birds wings with time before takeoff is modelled by $v = sin (100t^2+2)$. What is the acceleration after 0.5 seconds? Acceleration is the rate ...
24 views

### Differential equation of an object dropped from certain height

I want to solve this problem - A ball of mass 2kg is dropped from a tall building with zero initial velocity. In addition to gravity, the ball experience a damping force of the form -2v, where v is ...
1 vote
55 views

### Relation between "method of moving frames", spin connection, Cartan forms, and classic rotational kinematics in $\mathbb{E}^n$

I want to know how the "method of moving frames" involving things like connection 1-forms, torsion 2-forms, spin connections, etc. are applied to basic rotational kinematics in flat 3-space (...
1 vote
16 views

### Kinematic constraints and model of a tricycle [closed]

I am trying to solve an exercise which deals with the kinematic constraints and model of a tricycle, but I can't get the right answer. A front wheel driven tricycle has two rear wheels (1 and 2) which ...
68 views

### Velocity of Separation and Relative Velocity

I have some problems in understanding a concept, which has been used in the problem in the picture: I don't understand what are we actually using to solve this question. Are we using relative ...
38 views

### Is the way of determining my angle of vector wrong or am I using the wrong formula for calculating magnitude of resultant? [closed]

i) Two balls A and B are simultaneously projected from top of building at 10m/s upward and 20m/s downward. Find distance between them after 3s? (Answer: 90m) There are two magnitude of resultant ...
53 views

### (Circular motion) Acceleration is given, so why asked for more? [closed]

The full question is below. A car starts from rest and moves around a circular track of radius $32.0\,\text m$. Its speed increases at the constant rate of $0.500\,\text{m/s}^2$. (a) What is the ...
1 vote
135 views

### Can $d/t =$ speed ever be wrong? Is there a more accurate way to determine speed?

Is there a more accurate way to determine speed? I am asking because this has to do with an accident reconstruction where my son was killed. The investigators are trying to conclude his speed prior to ...
40 views

$a$=acceleration $v$=velocity $x$=position along x axis $t$=time instant My teacher derived the $a$=$v$$dv/dx formula as follows Assume a particle at time t is at x position having v velocity ... 3 votes 5 answers 156 views ### What happens physically when object is thrown up when v becomes 0 at max height? When velocity=0 during maximum height when an object is thrown up, what does that actually mean?? does that actually mean that the object doesn't change it's position over dt time period when at ... 0 votes 2 answers 52 views ### Why tangential acceleration become 0 when the velocity is max? I Know that tangential acceleration equal to zero when the circular motion is uniform, but why it is equal to 0 , when the velocity is max or min , because there is no relation between the value of ... 1 vote 3 answers 40 views ### Why is it that the normal force experienced as a object travels along a parabolic surface increases as compared to a flat surface? Is this because the surface 'comes up against' the object due to it's curved nature 0 votes 1 answer 61 views ### Velocity and acceleration of a ball shot uphill [closed] Consider a ramp of length 100 m and with a height of 10 m. At the base of that ramp we're shooting a ball of mass 12 kg uphill. Let's say the ball has a speed of 1 m/s at 1 m uphill. How can ... -2 votes 1 answer 62 views ### What is V in a=V$$dv$/$dx$? [duplicate]

$a$=instantaneous acceleration $V$=instantaneous velocity $x$=position $dx$=small Chang in position $a$=$dv$/$dt$ multiplying numerator and denominator by $dx$,we get $a$=$dv$.$dx$/$dx$.$dt$ now we ...
1 vote
25 views

### Kinematics problem involving two balls [closed]

I'm having trouble with a kinematics problem and was hoping someone could help me out. The problem goes like this: "A ball is dropped from rest from a point P on a tree branch 5 m above the ...
94 views

### Is there any physical difference between a receding body and a moving body? [duplicate]

Edited version. A body $A$ is receding at acceleration $\vec {a}$ with respect to a point $P$ because of the expansion of the universe. Another body $B$ is accelerating at the rate of $\vec{a}$ with ...
32 views

### Apparent rotation of a wheel [closed]

A wheel with 16 spokes rotating in the clockwise direction is photographed on film, The is passed through a projector at the rate of 24 frames/s, which is the proper rate for the projector. On the ...
23 views

### Linear and Angular kinematics for vehicle attitude and position estimation

I am building a robotics college level project, an unmanned aerial vehicle or a drone. I am using a mpu 6050 IMU for getting instantaneous acceleration and angular velocity of the system. I will be ...
68 views

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### Physical meaning of $dx/dt$ for objects of changing length

I was solving '200 Puzzling Problems in Physics' as a recreational activity and I encountered this beautiful question which surprised me as I understood a basic flaw in my conceptual understanding. ...
41 views

### Is the derivative of four-position with respect to an affine parameter for a light ray $c$?

The derivative of four-position with respect to proper time for a light ray is undefined, as light rays move along paths of unchanging proper time. However, would the derivative of four-position with ...
38 views

### Particle physics, alpha decay, & momentum mathematics question

Was reading through a physics textbook yesterday and came across a problem that I cant quite understand. Most of the question is clear to me but for the very last equation ( kinetic energy of alpha ...
98 views

### How to prove: Are perpendicular coordinates (wrt to relative velocity) unchanged (or only scaled) while deriving the Lorentz Transformations?

Thank you for helping with this question and I'm sorry if it's kind of stupid. TLDR: In many textbooks and other derivations deriving the Lorentz Transformations, they omit coordinate axes orthogonal ...
61 views

### Integrating Equations with Units - 2023

I have a worked example from a recorded lecture and lecture notes which I am having difficulty with regarding Rectilinear Motion in Mechanical Dynamics. When I asked my lecturer about the following, I ...
1 vote
98 views

### Linearization of an expression

I'm doing a physics lab and I have a question that asks me to linearize the expression of time (it gives me the equation for time) in function of the mass. I don't want any solution, just want to know ...
1 vote
93 views

### What is the link between normal acceleration and radius of curvature? [closed]

hope you are well, So , in my physics class we use graphical method to determine the radius of curvature and as we know this method isn't very accurate, so when I watch a YouTube video I find this ...
107 views

### $E_k = (1/2) mv^2$ doesn't make sense to me [duplicate]

I hope this is the right platform to ask stupid questions like this, but this is driving me nuts right now. Probably embarrassing to say, but I actually have somewhat of a physics background, but also ...
34 views

### Kinetic friction of a sled vs. static friction of a wheel

Since kinetic friction is lower than static friction, and a sled in motion experiences kinetic friction whereas a wheel experiences static friction, which one would go down a hill faster. Let's have a ...