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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531 views

Kinematics simple question [closed]

Question: In order to protect himself from the rain, a person is standing holding an umbrella at right angle to the horizontal surface. The rain is falling at 10m/s when the velocity of the wind is ...
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1answer
57 views

If an area remains at temperature 0 Kelvin would the area be frozen in time?

If an area is at 0 kelvin, I am guessing that there is no motion. Without motion in an area, will it not look as if time has stopped?
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2answers
51 views

Finding out the velocity [closed]

Displacement of an object is related to time $x=at+bt^2-ct^3$ where a, b and c are constant motion.Then the velocity of an object when it's acceleration is zero is given by ...
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2answers
1k views

Can these figures demonstrating the safety of “Archery Tag” arrows be correct?

There is a new sport called "Archery Tag" that involves shooting opponents with foam-tipped arrows fired out of a real bow. The official Archery Tag web site presents data that claims to show the ...
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2answers
3k views

Kinematics - projectile motion on inclined plane [closed]

Well I've tried everything to solve this problem, spent well over an hour, and have gotten no results. A particle is thrown over a triangle from one end of a horizontal base it grazes the top vertex ...
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3answers
371 views

Kinematics - Concept of average velocity [closed]

Average velocity, as I have heard, cannot be found simply by finding the average of two numbers. I have a question on average velocity, but am simply unable to proceed: A particle moving in a ...
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1answer
288 views

Kinematics - ball bouncing off vertical walls [closed]

So here's my best attempt to state the question: A ball is thrown from a 100 meter tall tower, which has a vertical wall in front of it. The initial velocity of the ball is 10m/s and the distance ...
2
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1answer
176 views

Kinematic, motion in 2D [closed]

If the kinetic energy at maximum height is 2/5 the kinetic energy at half the maximum height, find the angle of projection. In other words: K.E. at H(max) = 0.4*K.E. at 0.5*H(max) I got 60 degrees, ...
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1answer
165 views

Exeeding the speed of light by adding velocities [duplicate]

Well you know how it's said that things can't travel at or past the speed of light? However, can't they move at speeds greater than the speed of light relative to another object? For example: What ...
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3answers
150 views

Velocity and acceleration with displacement [closed]

Find the velocity and the acceleration for a moving object with displacement $= te^{-t}$. The $e$ is the exponential function.
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0answers
54 views

Geometric Interpretation of these equations of motion?

I was reading my Engineering Mechanics book, and it derived some strange looking integrals I'll have to apply. I could memorize them, but I'd rather understand them - then I won't have to memorize. ...
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3answers
238 views

average speed and velocity [closed]

A distance on a straight line from point $a$ to $b$ is $2 km$. A student walks from this line with a speed of 4km/h and another student walks with a speed of 6km/hour. what is the average velocity and ...
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0answers
76 views

how to calculate acceleration? [closed]

The problem is as follows. A searchlight casts a spot of light along the face of a horizontal wall located 100m above from the searchlight. It rotates at a constant $\omega$ of 4rads/s. Determine the ...
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1answer
176 views

Velocity at certain point?

I seem to have misunderstood something in velocity. There is a path from point A to point B, that gap between is 100 meters. An object moves from point A to B with a velocity is 10 m/s. ...
1
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1answer
135 views

Understanding why a problem was solved a certain way

I have this question in one-dimensional kinematics and the way the book solves it has left me confused. Here's the question: ...
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2answers
165 views

Why is initial position negative? [closed]

A student on ground throws a ball straight up, the ball leaves students hand with speed of 15m/s when hand is 2.0mm above ground How long is the ball in the air before it hits the ground? I was ...
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1answer
138 views

From 3D velocity to coordinates

I want to calculate the 3D position $T_x, T_y, T_z$ of an object with respect to a coordinate system if I have the mean velocity (norm) $v$ and its 3D rotation $(\omega, \phi, \kappa)$ with respect to ...
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4answers
685 views

Calculate average speed with unknown variable accelaration

I am in the middle of a vehicle tracking project where I have to calculate the distance traveled by the vehicle in a given amount of time. Data I am getting: ...
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2answers
156 views

Projectile motion - ball hit 180m/s at 45 degrees, what is the hang time? [closed]

Assuming no air resistance etc, how long is the ball in the air for? This is actually part of a longer question concerning the ball trajectory on different planets but I think there must be an easier ...
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1answer
202 views

Travel time for accelerating object [closed]

I have an object which starts at velocity = 0. Accelerates to a known max speed and continues thereon at constant velocity (max speed). My problem: How long does it take to reach a known ...
2
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1answer
64 views

The speed of an unconstant motion

There's already the solution for the problem but I still don't understand why the velocity can't be calculated by just $$ a = (v(t))'= -B_0 + B_1t \Rightarrow v(t) = -B_0t + 1/2B_1t^2$$ Also, both ...
6
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2answers
296 views

About photons and mirrors

If a photon hits a 'perfect' mirror (with no environment interference) would the mirror move a bit?
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0answers
78 views

How makes an equation to Flipping motion

Every now and then, I find myself reading papers/text talking about how this equation is a constraint but that equation is an equation of flipping which satisfies this constraint. Indeed, This ...
2
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1answer
511 views

How to get time from equation of linear uniformly accelerated motion? [closed]

I have had a problem solving this equation for time (from Linear Uniformly Accelerated Motion (LUAM)): $$ s= v_0t + \tfrac{1}{2}at^2 $$ I'll appreciate if someone could provide me some step-by-step ...
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2answers
2k views

Average velocity = Arithmetic Mean [duplicate]

I am having trouble grasping how the average velocity of a particle between an initial position and final position equals to the arithmetic mean of the initial velocity and the final velocity when the ...
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1answer
577 views

Kinematics - angle of projection given relation between speed at highest point and half of that [closed]

For a projectile launched from a point on horizontal ground, the speed when it is at the greatest height is $\sqrt{\frac{2}{5}}$ times the speed when it is at half of its greatest height. Determine ...
2
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3answers
2k views

Getting position from an accelerometer on an Android phone

I know that integrating acceleration twice will give me position (acceleration-->velocity-->position) but how can I do all this when I all I have are a set of data points (ex: 1 second = some # ...
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2answers
557 views

Help with a solid sphere sliding and then rolling

Initially at time $t=0$, a solid sphere slides with velocity $v$ along a horizontal surface. The coefficient of friction is u. Find the required time for the sphere to stop sliding (the sphere will ...
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3answers
446 views

Displacement of a body in free fall

Suppose a ball is thrown up from the ground with some velocity. Let vertically up be the positive direction and vertically down be the negative direction and let the thrower be at the origin. What ...
9
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4answers
56k views

What is the relationship between kinetic energy and momentum?

I can't seem to figure out the relationship between $E_k$ and $p$ or $F$. I understand that the units are pretty different. But for example: A bullet with a mass of 10.0g is moving at the speed of ...
11
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2answers
26k views

Difference between momentum and kinetic energy

From a mathematical point of view it seems to be clear what's the difference between momentum and $mv$ and kinetic energy $\frac{1}{2} m v^2$. Now my problem is the following: Suppose you want to ...
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1answer
39 views

Can the thermal energy in an object be aligned, creating a thermal jerk?

Thermal energy is related to the speed at which atoms vibrate, therefor thermal energy is a form of motion. In a stationary object, all of these vibrating atoms 'impact' each other in such a way that ...
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1answer
2k views

Throwing an object in the air [closed]

Studying formulas about velocity and acceleration I came up with a question: if I throw an object in the air with a velocity $v_0$ (suppose i throw it vertically) in how much time its final velocity ...
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3answers
201 views

How to calculate the velocity of this body? [closed]

Graph of a train (the body) is provided which starts from rest. What is the velocity after the train has 10 metres displacement? Thats the only things provided for the question, please help me ...
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2answers
178 views

Is there a mistake in this example in my mechanics textbook?

This is a worked example in my mechanics book: But I think this worked example is wrong. In the 6th line. shouldn't $X=4R$ as the expression for distance above the surface is $(X-R)$ and when the ...
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0answers
87 views

snails moving on a sphere [closed]

I am trying a variation of snails moving in an equilateral triangle. Suppose that you have $6$ snails arranged on the the surface of a sphere such that they are equidistant from each other. All the ...
0
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1answer
112 views

Question about pendulum

I came up with this problem by myself: How much force do I need to make a pendulum revolve? Now I imagined that the force $\vec{F}$ must be enough to make the pendulum swing until half of the ...
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1answer
190 views

Estimating the weight of a vehicle moving in a highway [closed]

I need to know the estimated weight of a truck in a highway without using scales. What do I have? Speed of the car at time X RPM at time X horse power Estimated distance from a point A to B ...
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2answers
2k views

Why does a perpendicular force not change speed?

I have been taught that a perpendicular force acting on an object will only change the direction of its velocity, not its magnitude. The explanation that was provided to me is that because there no ...
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1answer
600 views

Angular distance Vs Angular displacement

Are the two terms - 'Angular distance', and, 'Angular displacement' interchangeable for a uniform circular motion?
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2answers
76 views

Kinetic energy of a mass rotating about two axes

I'm working on a question where I have to find an equation for the kinetic energy of a mass being rotated by a fold-able arm. The equation for $m_1$ is obvious, however, the equation I derived for ...
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6answers
7k views

Ion Drive Propulsion Top Speed

I would like to know if there is some formula / graph which would provide / show the efficiency of a certain type of propeller in space. Specifically, I'm interested in the acceleration attainable at ...
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0answers
183 views

Uniform Circular Motion with Banked Road and Car [closed]

In Uniform Circular Motion, if a car is rounding a curve at a certain speed, and the angle of the road allows the car to drive around at that speed, that speed is called the "design speed." If the ...
0
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1answer
420 views

Horizontal projectile motion, finding the height of the object at a given time. [closed]

A canon is fired Horizontal to the ground 80 meters above ground The canon ball is fired a $T=0$ and hits the ground at $T_g$. Calculate the height at the time $T_g/2$ So far I have calculated time. ...
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1answer
111 views
0
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1answer
117 views

Pendulum Confusion

This text in my book is pretty confusing:With my emphasis A simple pendulum is a heavy point mass (bob) suspended from a rigid support by a massless and inextensible string. This is an ideal case ...
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2answers
172 views

When solving kinematics questions, how to find time in air?

I was trying to help a friend with this question: A ball is shot horizontally off a cliff. What would happen to the horizontal distance it travels if the acceleration due to gravity were doubled ...
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1answer
396 views

Equations of motion of particle mass on parabolic surface

Given a parabolic surface $$ Z = \frac{\Omega^2}{2g}\left(X^2 + Y^2\right)$$ My textbook (Introduction to Geophysical Fluid Dynamics, 2nd ed, p.50) states: "Provided that the paraboloid is ...
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0answers
155 views

Kinematics and Motion [closed]

If a body loses half of its velocity on penetrating 3cm in a wooden block, then how much will it penetrate more before coming to rest? How does answer come out to be 1cm?
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2answers
64 views

Motion of two gravitational bodies?

I'm doing a basic realtime simulation of two bodies, but the orbits are unstable for some reason. This code is run at every timestep: ...