# 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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### Why cant the range of a projectile be calculated as the horizontal velocity multiplied by the time it takes the projectile to fall?

If I am given an angle, initial velocity, and initial height, I can calculate the time it takes for the projectile to hit the ground by using -(initialHeight) = Voy(t) - 5t^2. Now that I have the time ...
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### $t=0$ is out of the domain of the equation of motion

At $t=0$, $Q_1$ is dropped under the influence of only the electrostatic force. I have solved the differential equation to find the equation of motion: and the distance of the 2 objects as a ...
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### Newton first law of motion

The State of rest and the state of uniform linear motion are equivalent. Why?
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### Classic River swimmers problem [closed]

The problem states that Two persons at the bank of a river start swimming simultaneously at the same speed with respect to water. One person swims perpendicular to the stream in such a direction that ...
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### Hurricane - trajectory in a logarithmic spiral

Let $f : [0,\infty[ \longrightarrow [0,\infty[$ be a given function and consider a particle on the plane such that the particle starts at point $p_0$ at time $t=0$, its trajectory $t \mapsto p_t$ is ...
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### Integrating product of Dirac deltas and step functions [closed]

I have the following integral $$\int d^4\boldsymbol{x}' \,\delta\big[(\boldsymbol{x}-\boldsymbol{x'})^2+\alpha^2\big]\,\Theta(-x_0+x'_0)\,\delta\big[(\boldsymbol{x'})^2+\alpha^2\big]\,\Theta(-x_0'),$$ ...
549 views

### Greatest distance between a particle moving with constant velocity and a particle moving with constant acceleration

Two particles start moving along the same straight line starting at the same moment from the same point in the same direction. The first moves with constant velocity $u$ and the second with constant ...
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### Slow down object to given speed in given distance [closed]

I have a problem. I have this data: my speed: 100km/h destination speed: 50km/h braking force: 8000N How to calculate distance needed to slow down my object? I dont want to look at other forces. ...
35 views

### How to use Whewell equation to find Velocity and acceleration? [closed]

Question How to use the following information to answer this question? $$\vec{v}(t)=\vec{r} '(t) ,\qquad \vec{a}(t)=\vec{r}''(t)$$ My attempt to answer this question.
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### Why intuitively is the tangent vector the derivative of velocity of position with respect to their modulus?

When trying to find the tangential velocity, many textbooks define the tangent direction as one of the following: or Intuitively, why is the tangent vector the derivative of the position with ...
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### Trivial uniform acceleration motion question [closed]

There is a question which to me (someone who knows very little physics) sounds a bit easy to solve, but I can't figure out what I did wrong here. QUESTION A person climbs 800 meters per hour. After ...
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### Speed of atoms being pushed away

It is said that it is impossible to calculate one-way speed of light. I have doubts in my small theory and I would like someone to correct me because I lack in knowledge in physics, and I'm surely ...
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### Some introductory 1D falling motion problems to check the answers to [closed]

So I have the following problems for an introductory mechanics course (AP Physics C in high school, if anyone is familiar with it), and I got the following answers (using g = 10). Can someone check ...
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### If the earth spins at roughly 1,118.4 mi/h and you are speeding down the highway at 115 mi/h, what does a cop's radar read? [closed]

Hypothetically, if the earth spins at roughly 1,118.4 mi/h and you are speeding down the highway at 115 mi/h, what does a cop's radar read? Also, if the earth is spinning at 1,118.4 mi/h and you are ...
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### Converting jerk function of distance to jerk function of time [closed]

When free falling inside a gravitational field, the jerk as a function of $r$ (the distance from the center of the Earth) is $$j(r)=\dot{a}(r)=-\frac{2GM}{r^{3}}.$$ Now suppose we have an apple that ...
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### For the given motion of the object in the velocity-time graph, which of the following relations are true? [closed]

The velocity-time graph of a particle in one-dimensional motion is shown in figure. Which of the following formulae are correct for describing the motion of the particle over the time-interval $t_{1}$ ...
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### Kinematic question

I am trying to solve Problem 1.20 from Kleppner and Kolenkow book on Mechanics: Their solution is: which I understand. Notice that this results in $t_0 = 10.08s$ and $t_1 = T-t_0 = 12.50s$. However,...
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### Displacement and distance for a particle travelling in straight line [closed]

A particle travels along a straight line with a velocity $v= (12 - 3t^2)$ m/s , where $t$ is in seconds. When $t$ = 1 s, the particle is located 10 m to the left of the origin. Calculate displacement ...
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### How to translate force into upward hinging motion between two panels? [closed]

How to create a hinged joint between two panels where the hinging motion is actuated simply by pushing the panels together as they lie flat? Pictured below are two hinged panels that can rotate upward ...
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### How do we know if a particle is moving or not?

if there is only one particle in the universe, how do we know if it is moving or not? We don't have any other object to track the distance between the two, then is it possible to determine the ...
41 views