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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1answer
18 views

Finding the average speed plus a break [on hold]

I have the following equation when the driver drove 2.5h at 120 km/h and then stopped for 30 minutes. Then he drove for 20 minutes at 25 m/s. The result of the equation is to determine the average ...
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1answer
27 views

Direction of acceleration vector at the apex of a curve

(Test Your Understanding of Section 3.2) The question wants me to choose the correct acceleration vector, from the given 9 options where 9th option is zero acceleration. Ok, first I thought option ...
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3answers
42 views

From the frame of reference of a colliding object, does the entire universe change direction when it bounces?

Consider three objects: a rubber ball, a spaceship, and an isolated brick wall floating serenely in the vacuum of space. From the perspective of an observer on the spaceship, the ball is moving ...
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Help With a Projectile Motion Problem [on hold]

So I have what seems to be a fairly easy projectile motion problem that I just can't solve, I believe I am using the wrong idea and am requesting help! The problem is as follows: A boy on the edge ...
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8answers
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Is there any physical evidence for motion?

Let's say that we have 2 tennis balls in space, one being in motion (say, pushed by an astronaut), and the other one still. If we could take a snapshot of both tennis balls, would there be any ...
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1answer
18 views

The velocity of an object leaving the inclined plane

I saw the question below in our physics textbook. It asks A block of mass m is released and slides down on the frictionless inclined surface ( the inclined plane is of concrete and doesn't ...
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2answers
32 views

What are two different angles we can throw a ball, so it lands at the same spot? [on hold]

This is not a particularly difficult task, but it has given me a lot of trouble and I can't solve it. We throw a ball at 60° angle with a speed of 20 m/s. The ball lands 35.2 m away. What is the ...
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Energy spectrum of photoneutrons

In "Radiation Detection and Measurement" Knoll considers the production of neutrons by a ($\gamma$, n) reaction such as \begin{align} \gamma + \ ^{2}_{1}\text{H} \rightarrow \ ^{1}_{1}\text{H} + n &...
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I want to learn the behavior of rotating bodies thrown in the air

Could anyone suggest me a paper that could help me on that? ( That describes it mathematically. )
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1answer
17 views

Tangential velocity after ball strikes wall

I have to solve a problem where there is a ball that goes in the perpendicular direction towards a wall. It strikes the wall and goes back at the same angle it came from. (All the movement are ...
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1answer
17 views

kinematics: Angular velocity [on hold]

What is angular velocity when an object rotates through half a revolution in clockwise direction and then rotates through half a revolution in counter clockwise direction to reach the final ...
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2answers
32 views

Kinematics: Circular Motion

What is the difference between angular velocity and angular speed? Is angular velocity after one complete rotation zero? Is the magnitude of angular velocity always equal to angular speed?
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Finding initial velocity of balls [on hold]

Ball A is released from rest at height h above the ground. At the same time, ball B is projected vertically upward with initial velocity u. After some time, two balls are at the same height above the ...
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1answer
43 views

How do you derive $v_f^2 = 2ad + v_i^2$ from $v_f = v_i + at$ and $d = v_it + (a/2)t^2$?

I'm trying to use substitution to find the equation Vf^2 = 2ad + Vi^2 from Vf = Vi + at and d = Vit + a/2(t^2), but I get stuck understanding part of the math. I've attached a picture, and you can see ...
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1answer
55 views

How does relative motion theory adjust other variables than kinematics' basics like velocity or displacement?

I have been confused on this concept for a while - suppose a boy is going from east towards west with some velocity on a bicycle and rain is falling in a vertical downwards direction. Then, if we ...
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2answers
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${}$ Kinematics: One dimensional motion [on hold]

Above is the speed-time graph of a particle in motion along a constant positive direction, as per my textbook accelration in the interval 3 is positive. But I think acceleration in the interval 3 is ...
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0answers
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Hemispherical bowl problem..kinematics [closed]

A particle P is sliding down a frictioness hemispherical bowl.it passes the point A at t=0.At this instant of time the horizontal component of its velocity is v . A bead Q of the same mass as P is ...
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1answer
37 views

Parabolic trajectory with several unknowns [closed]

I have a problem where I need to find out the launch angle alpha of the parabolic trajectory that extends beyond y = 0. The only known variables are g = 9,81m/s^2, x1+x2 = 2.5 m, y2 = 3 m and v0 = 4 m/...
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2answers
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Acceleration of a Bouncing ball when it hits the ground

The conceptual problem I am having difficulty with is something like this: If a bouncy ball is dropped from some height $h$ and rebounds to a height of $0.75h$ in some time $t$ (for example), what ...
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2answers
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Does slope of $y$ vs $x$ curve tell anything about magnitude of instantaneous velocity at that point?

I know that slope at any point on the trajectory of a moving body gives us the direction of its instantaneous velocity. Does it tell us anything about magnitude of the velocity at that point? I don’...
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Basic Kinematics Help [closed]

I've been trying to figure out this problem for quite some time and i don't know where I am going wrong? Seems I have everything lined up correctly?
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2answers
97 views

Velocity of a ball rebounding off a moving train

At the bottom of this page says (my emphasis): It's interesting to note the speeds in the cartoon. The propeller-beanie kid sees his tennis ball moving away from him at 30 miles per hour. So ...
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2answers
54 views

Kinematics: One dimensional motion

If a particle is moving in one dimension with constant speed, can we say acceleration is zero at all the points? Answer given in my textbook is yes acceleration is zero. But I think it can undergo a ...
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5answers
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Why do these two ways of understanding constant acceleration give different results?

I have a question pertaining to the concept of acceleration and it's formula - Both seem to give me different answers. I was asked: A train is moving at a velocity of $20\ \mathrm{m/s}$. It hits ...
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0answers
19 views

What is the height of the cliff? [closed]

The initial launch velocity v0 of the balls is 100 m/s, the green ball is launched at an angle θ=30°, and the balls land 600 meters apart from each other, what is the height of the cliff? (Note: ...
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Any nice solutions to this kinematics problem? [closed]

So I made a mock F=ma exam with a couple of my friends on AoPS. Here is one of the problems (problem 21) Bob lives in the universe $\Omega$, which happens to be a physics simulation. In $\Omega$,...
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1answer
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Rotation of top of symmetries

while learning about rotation, I started to wonder what forces will come into play. Lets picture a top with two masses centered at (-1,0,-1) and (1,0,1) with rods connecting the masses directly to the ...
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1answer
20 views

Wind is blowing against a plane, what direction should the plane head towards to end up at the airport?

A plane is flying with a speed of 550km/h with respect to the air hoping to land at an airport due south. There is a strong wind blowing at 68km/h against the plane at 30 degrees [N of W]. What ...
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0answers
60 views

Converting velocity vector formula from Cartesian coordinate system to polar coordinate system

I have a little question about converting Velocity formula that is derived as, $\vec{V}=\frac{d\vec{r}}{dt}=\frac{dx}{dt}\hat{x}+\frac{dy}{dt}\hat{y}+\frac{dz}{dt}\hat{z}$ in Cartesian Coordinate ...
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35 views

What is the equation of motion of the path of a bowling ball? [closed]

What is the equation of motion of the path of a bowling ball and how exactly is this found?
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1answer
36 views

Meaning of normal acceleration?

acceleration means the rate of change in velocity (vector quantity) and the differentiation means to divide a certain quantity into small elements (i.e $dx$) as we do to find the acceleration at any ...
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3answers
69 views

What is the effect of acceleration due to gravity on horizontal acceleration?

The question is the following: An object accelerates from rest to $100\,\mathrm{km}$ per hour in $4.0\,\text{seconds}$. What fraction of the acceleration due to gravity is the car's acceleration? ...
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1answer
37 views

How do I derive the formula for radial acceleration when there is no uniform circular motion? [duplicate]

My lecturer states that $a_r=\dfrac{v_t^2}{r}=\omega^2r$ where $v_t$ is tangential velocity, he also wrote that this is derived the same way that radial acceleration is derived in uniform circular ...
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4answers
106 views

Why the need for defining the velocity as a derivative? [closed]

Something intuitive and fundamental as the concept of velocity (of a particle for example) in classical physics is defined as a derivative, a concept to me quite vague and strange, although i know its ...
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2answers
40 views

How is energy conserved in terms of “Work”

Basic equation of work is given by $F\cdot s$. When work is done, the energy is stored either in form of potential or kinetic. My question arises when we look at a case of applying $m g$ of force ...
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2answers
76 views

1D falling object, and terminal velocity

I'm simulating a very simplified scenario of a missile falling to earth after being deployed at altitude. Currently I'm evaluating 1D only assuming the missile has already turned and is in a stable ...
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19 views

Relative velocity problem trick

There used to be a river man problem where the swimming speed of man in still water was provided along with speed of river current.Now we had to find the angle at which he should swim for minimum ...
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1answer
49 views

Why do we neglect $\Delta t^2(\frac{d\vec{r}}{dt}\frac{d\vec{\hat{r}}}{dt})$ at Taylor Expansion?

I'm just started to Ankara University Physics Department two weeks ago. I have missed my 2 hours of PHY105 course that is the last week Wednesdey. The subject that i missed was Derivatives of Vectors. ...
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1answer
61 views

Can one find the uncertainty of a particle from Schrödinger's wave equation? [closed]

Right now I am studying quantum mechanics and I'm having trouble understanding what exactly $\Psi$ is in Schrodinger's equation $\Psi(x) = A\sin(kx) + B\cos(kx)$. After doing some googling I learned ...
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1answer
57 views

How is do you say the “standard acceleration of gravity, $g=9.80 m/s^2$” in words? [closed]

How is do you say 9.80 m/s^2 in words? (I Don't get if only "the second" is squared or the whole thing is squared or just the m/s is squared)
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1answer
40 views

What parameters affect the range and flight path of playing card? How?

An ordinary playing card can fly quite a long distance if you spin it during a throw. What parameters affect the range and flight path? How?
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1answer
61 views

Understanding Average Velocity's Logic

Firstly, I'm a new learner of physics. I'm a bit confused about average Velocity's logic. There is a problem that I am trying to solve as the following : You walk $73.2$ m at a speed of $1.22$ m/s ...
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1answer
26 views

Finding height and speed [closed]

A small puck of mass m glides along a smooth horizontal table at a speed v0 to a shiftable slide of mass 3m that is at rest, the puck up the slide with no friction and then glides down the slope in ...
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3answers
46 views

Centripetal acceleration on frictionless plane

Suppose I have circular, frictionless disk, and in the center of the disk there is a small box. The disk is then rotated. I gently push the box to disorient it from the center. Will the box accelerate ...
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0answers
71 views

What am I not understanding about this double integration of acceleration to get position?

Brilliant.org has a module on classical mechanics and I'm having difficulty with a mathematical step. They want you to represent position in terms of acceleration and then to solve the double integral ...
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2answers
14 views

Spring mass damper system: Distance from equilibrium after applying velocity to mass

I have a spring fixed to a wall on one end and a mass object on the other end in its natural resting position. The question is how far does the spring stretch when a velocity $v_0$ is applied to it, ...
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1answer
49 views

Computing total derivative of Kinetic Energy w.r.t time

I am confused as to how to take the total derivative $\frac{dKE}{dt}$, where $KE$ is the kinetic energy. I know that $KE = 1/2 *m * \dot{\vec r} \cdot \dot{\vec r}$. From here, if I take derivative ...
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1answer
52 views

What is the significance of infinite acceleration in this case? [closed]

the Question is as follows: Pick the correct statement: (a) The average speed of a particle in a given time is never less than the magnitude of the average velocity (b) It is possible ...
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1answer
48 views

cant this question be solved other then the method involving integration and differentiation? [closed]

the question was : A particle moves along the X-axis as $$x=u(t-2s)+a(t-2 s)² . $$ (a) the initial velocity of the particle is $u$ (b) the acceleration of the particle is $a$ (c) the ...
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3answers
47 views

Should not the acceleration acting on the stone being dropped be $a$ as well along with $g$?

the question is: A stone is released from an elevator going up with an acceleration a. The acceleration of the stone after the release is (a) a upward (b) (g-a) upward (c) (g-a) ...