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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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### How can momentum but not energy be conserved in an inelastic collision?

In inelastic collisions, kinetic energy changes, so the velocities of the objects also change. So how is momentum conserved in inelastic collisions?
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### Frame of Reference in Kinematics

If we have two frames of reference, say S1 and S2, and the acceleration of a particle as seen from both the frames has equal magnitude, say 4 m/s^2, then shouldn't the frames have no relative ...
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### Stanley kinematic model controller

I am having problem calculating delta (steering angle). L is the length of vehicle lfw is distance between rear and center of vehicle. eta is the angle between direction of the vehicle and target on ...
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### 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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### 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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### How do i calculate the speed of the ball? [on hold]

A spring pushes a 15 grams ball with 10 m/s in a bent pipe. What is the formula to calculate the speed of the ball in point A and point B. The pipe is horizontal so there is no g-force and the pipe ...
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### Question is in description [on hold]

If a volleyball gets served at a height of 2ft at 15m/s from one side of a 60ft court over a 7ft net, what angles will make the ball travel the whole court exactly?
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### Average acceleration [on hold]

The space shuttle Discovery has made 30 flights. The space shuttle is approximately 37 meters long and has a wing width of 24 meters. The three main engines of the space shuttle are used when ...
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### 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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### Finding initial velocity of balls [closed]

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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### Classical Relativity: Clarification

I am working on a problem that states: "A swimmer capable of swimming at a speed $c$ in still water is swimming in a stream in which the current is $u$ (which we assume to be less than $c$). ...
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### 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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### 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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### The instant an accelerating object has zero speed, is it speeding up, slowing down, or neither?

This problem is from Khan Academy. Specifically for the blue point circled in red, the answer is that at this blue point, the object is neither speeding up nor slowing down. When I think about the ...
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### ${}$ Kinematics: One dimensional motion [closed]

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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### 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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### 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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### 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’...
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 $\Omega$,...