# 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 does conservation of energy differ from conservation of momentum in this problem?

Here’s a problem and how I used two approaches: https://ibb.co/r47C0gG In the problem, I’m assuming there is no friction, so all energy and momunetum is conserved How come the KE method isn’t the same ...
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### Finding motorcycle turning radius based on lean angle

I have been implementing a basic motorcycle physics model and have been predicting the turning circle of both wheels based on the current angle of the front wheel. However, this fails to predict the ...
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### Kinematics find time ratio

I am learning physics for my upcoming exams and have this practice question. I am stuck with this and do not know how to proceed from here. Can someone assist me? A boat travels in a straight line ...
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### Why is instantaneous velocity tangent to trajectory?

Trajectory is the path of an object through space as a function of time. However, in many trajectory plots, when the movement is planar, a horizontal position axis and a vertical position axis are ...
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### In Radius of Curvature calculation why do I have to assume $\text{d}^2x/\text{d}t^2=0$?

Recently, I was calculating the radius of curvature of projectile trajectories at certain points. There are two ways to do the same: Given the velocity and acceleration of the particle at some point, ...
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### What direction should i exactly put for negative displacements?

If I have A....p....B....d....C points If I am initially on B and walk towards c, it's a positive displacement. Example: BC=10m east and then all of sudden I change my vector and walk to d. Is ...
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### Must trajectory of an object with constant velocity angle relative to displacement be a line or circle?

Imagine you have a point object moving on the plane with its position as a function of time $$r(t)=\langle x(t),y(t)\rangle$$ Suppose that for any instant $t$ and time interval $\Delta t$, one has ...
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### Finding the time period under variable acceleration

"A moves in a circle of radius $R$ such the it's tangential and centripetal accelerations are always equal in magnitude. It's inital velocity is $v_0$. Find the time period of the first ...
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### What's the difference between using $a=(v2-v1)/t$ and $s=u\cdot t+1/2\cdot a\cdot t^2$?

I have a coilgun shooting a projectile at initial velocity=0. We tracked the final velocity by dividing distance (0.5m) by time (0.13s) from exit of coilgun to impact 0.5m away with a camera. So: v2=0....
1 vote
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### Finding the average speed of an object going down curved slides of different sizes

Say I have a slide that starts at point A which is h meters above the ground. The slide ends at point B, which is at ground level and l meters from A (horizontally). The length of the slide is L. The ...
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### Shock testing equations (oversimplified?)

I'm designing a shock test tower with a maximum drop height of 1.8m. I'm adding bungee cords to add impulse and reach the intended 150G as it hits the programmer at the bottom. My question is, is it ...
1 vote
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### Can we have motion in systems where inertia is neglected? [closed]

According to Newton's law: $$\sum F=ma$$ So, if we have some acceleration, it's because we have a certain amount of motion in our systems. This makes me confused if inertia was neglected. Are there ...
1 vote
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### Why doesn't an air valve move automatically when placed on a zero friction surface?

Air pressure is actually a force experienced by the surface of the container when air molecules hit it in high speeds. An air valve opens and allows air to move in one direction and blocks the the ...