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
177 views

According to Newton's third law, why don't Action and Reaction make equilibrium? [duplicate]

According to Newton's third law, Action and Reaction are equal and in opposite direction. If both forces are equal and in opposite direction then why they don't make equilibrium and void the effect of ...
-1
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1answer
3k views

Finding the point of collision between two objects when acceleration is constant

$\newcommand{\accunit}{\mathrm{m}/\mathrm{s}^2}$ A coin is dropped 60.0m above the top of an elevator car. The coin is dropped just as the car begins to move upwards. The elevator first ...
0
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1answer
61 views

Uniform Acceleration [closed]

A steel ball is allowed to roll from rest down a 20.0 m long slop and over a 25 m long level surface. It takes 4.0 seconds to roll down the slope. Calculate the speed at the bottom of the slope. ...
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1answer
1k views

Calculate Mass based on Velocity and Acceleration

I am attempting to design a obstacle avoidance system with the Arduino. My position (for now) is going to be stationary. I will be detecting an incoming object and I want to use the below known ...
2
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1answer
198 views

Dog running after sephard

Assume there is a dog A on a field and a sephard B. B moves on straight line with constant ...
0
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1answer
2k views

Projectile motion, what is the relation between initial angle and speed at a given distance [closed]

I am trying to understand the relation between the initial angle of a projectile and its initial speed, given that the distance this projectile will travel is fixed and at the same height as the ...
0
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0answers
51 views

The electron and classical dynamics

Can I use Newtonian laws of dynamics and kinematics applied to electrons (like $F = ma$ and $s = s_0 + v_0 t + at^2/2$)? If not, why not? I know that everything in principle behaves in a quantum ...
2
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0answers
191 views

Air resistance of a general shape object

I'm trying to code a simple physics simulator in C++ but I'm stuck on the air resistance issue. Surfing the Internet I only find a drag coefficient for very basical area shapes when the air is ...
2
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1answer
461 views

Vertical circular motion followed by projectile motion

If you have a stone tied to a string, and it is given a certain velocity at the lower most point such that it completes a quarter circle but then the string becomes slack, and it undergoes projectile ...
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2answers
2k views

Can you help me solve a difficult kinematics problem? [closed]

I've been working on this problem for a while now, but I still don't know how to solve it. It involves 2D kinematics, which aren't in themselves hard, but this one threw me for a loop. A ball is ...
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0answers
365 views

How to find the angle of elevation and launch speed? [closed]

A particle is projected from a point on level ground with a speed of $u$ meters per second and an angle of elevation $\theta$. The maximum height reached by the particle is $42$ meters above the ...
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1answer
146 views

Investigation of a pendulum's period, problem creating equation to sum the dynamic velocity

I am investigating the period of a pendulum swing. This is a simple harmonic pendulum and I am already aware of the common, but slightly inaccurate, $2\pi \sqrt{\frac{L}{G}}$ formula. My problem is ...
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1answer
537 views

What is the greatest speed he can reach with an acceleration of 5.00 g before blacking out? [closed]

A jet fighter pilot wishes to accelerate from rest at 5.00 g to reach Mach-3 (three times the speed of sound) as quickly as possible. Experimental tests reveal that he will black out if this ...
0
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1answer
71 views

Asking the vector form of the equation about velocity

In the undergraduate text of physics, the equation for velocity and displacement at constant acceleration are given in scalar form. For example, my text reads $$v^2 = v_0^2 + 2a(x-x_0)$$ But today, ...
0
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1answer
177 views

How long does it take for the speed of the train to decrease to $1~\text{m/s}$?

Here's the full problem: The speed of a train coasting on a level track satisfies the differential equation $\mathrm{d}V/\mathrm{d}t = kv^2$. The initial speed of the train is $v(0)=10~\text{m/s}$ ...
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3answers
682 views

How do I meaningfully divide by a vector?

How long does it take a baseball with velocity $(30, 20, 25) m/s$ to travel from location $r_1 = (3, 7,−9) m$ to location $r_2 = (18, 17, 3.5)m$? I am thinking that it should be the ...
2
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5answers
225 views

How does this shell hit the aircraft?

A fighter aircraft is flying horizontally at an altitude of 1500m with speed of 200m/s. The aircraft passes directly overhead an anti-aircraft gun. The muzzle speed of the gun is 600m/s. ...
5
votes
2answers
155 views

View from a helicopter rotor: why is the horizon distorted?

This video ("rotor panorama") was captured by a camera attached to the rotor head of a radio-controlled helicopter, with the frame rate set to the rotor's frequency. During a long segment of the ...
2
votes
2answers
593 views

Conservation of linear momentum magnitude along a trajectory

I was once criticized for "taking angular momentum as momentum going in a circle". I was loosely trying to state, in classical mechanics, that in using conservation of momentum, one can switch between ...
1
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1answer
170 views

If the velocity of particle $A$ exceeds that of $B$, is the acceleration of $A$ greater than $B$?

Two particles $A, B$ are travelling along parallel straight paths. At some point, the velocity of $A$ exceeds that of $B$. Does this necessarily mean that the acceleration of $A$ is greater than the ...
0
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1answer
358 views

Centripetal acceleration for particle that moves in a circle at non-constant speed

How is $a_{R}=v_T^{2}/r$ derived for changing tangential speed? ($a_R$-centripetal component $r$-distance from axis $v_T$- tangential speed)
5
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1answer
238 views

Walking along a moving train, we make 18 steps. Opposite: 11. How long is the train?

A man walks in the same direction as a slowly moving train ($v_{man} > v_{train}$). He counts the train to be 18 steps long. Then he turns around and counts the train to be 11 steps long. ...
0
votes
1answer
85 views

Find the distance from the initial location [closed]

Sing Huat drives a car with initial speed 30 km/h and acceleration 2 km/h2 toward Tee, whose displacement is 200 m away from him. At the same time, Tee drives another car toward Sing Huat with ...
-2
votes
1answer
163 views

Rigid Body Mechanics In a vacuum (no gravity) [closed]

I am writing a physics engine to map the rotary and translatory movements of a uniformly dense solid cylinder within 3d space. If a vectored thrust is applied to one end of the cylinder at an ...
0
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3answers
2k views

Calculating acceleration function for given time, distance, initial velocity [closed]

An object has an initial velocity of v and should stop in d meters, in t seconds where v*t >= d. I can predict that this acceleration won't be constant but it is a function of time and this problem ...
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2answers
281 views

Measuring the velocity of a pendulum using the width of the bob

I did an experiment on pendulum motion and in the method it says use the following equation to measure the velocity of the pendulum: $$v=\frac{W}{t}$$ where $W$ is the width of the pendulum bob and t ...
0
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1answer
171 views

Projectile maximum height [closed]

How can I determine the needed initial velocity to make a 2d wind resistance free projectile (in computer simulation) reach maximum height at a certain x distance away, with launch position and target ...
0
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0answers
376 views

Is it possible to solve a 2D relative motion question using components of relative velocity?

This is a question based on concepts of two dimensional motion . Here's how the question is: A plank A is floating in air, gravity has no effect on it (See its coordinates in the figure attached). ...
2
votes
1answer
149 views

Average Velocity [closed]

A car travels 100 miles in 2 hours, it then completes the return leg of the journey. How fast must it travel on the return leg to average 100mph over the total journey. My thoughts on this are that ...
0
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1answer
142 views

Obtaining velocity or acceleration vector of a point on a rigid body?

If I have a cube that is moving at a velocity of $v$ and spinning at an angular velocity of $\omega$, how can I determine the instantaneous velocity vector of one of the vertices of the cube? What if ...
2
votes
1answer
2k views

Is squared motor gearbox ratio proportional to inertia ratio?

I read an interesting article http://m.machinedesign.com/news/motor-sizing-made-easy It is very interesting, but I can not follow the 2nd last paragraph. I don't understand why it is true. ...
0
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1answer
127 views

Kinematics problem

I'm on earth and we have two spaceships $A,B$. They can instantaneously accelerate to certain velocities $v_A,v_B$. We want to travel to another planet which is $\Delta x$ lightseconds away, and we ...
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2answers
849 views

Projectile Motion Question involving a ball and a ramp inclined at an angle

The question is to finde the initial horizontal velocity of the ball at end of the ramp, where it is released. I know how to do this using gravitational potential energy and kinetic energy ...
0
votes
1answer
144 views

$d=\frac{1}{2}at^2$ not giving expected results

Say I have an object that starts falling from rest at 2 m/s2. Its total displacement and velocity at the end of every second should look something like this: ...
0
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3answers
86 views

Is it possible to reach the edge of a room if there isn't any gravitational acceleration?

Consider that a large room(an indoor badminton court) is orbiting the earth with a person floating exactly at its center without any relative initial velocity. Consider that the person has no ...
0
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1answer
159 views

Find shadow's height

Just starting to learn physics. Now reading about constant motion and after this paragraph I have a task: Boy with growth of 1.5 m runs at a speed of 3 m / s in a straight line, passing under a ...
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2answers
223 views

Steering forces on a bicycle

Ok, I always notice this weird thing and try to overcome it but cant. Ok as shown in the image when I ride the bike by just one hand and pull the handle back say from the right side so as commonly the ...
1
vote
1answer
291 views

1D Motion under Gravity

I have attempted this question in so many different ways but I am getting nowhere. Could someone point me in the correct direction so I can work it out myself? Here is the question: An object $K$ ...
2
votes
1answer
88 views

Are there bounds or measurements on the derivative of acceleration (jerk)

The title says it all. Is there a physical maximum value to the 3rd derivative of position? Common Lore says that there is not and that jerk does not play any role in physics. My guess is that there ...
2
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2answers
1k views

Average velocity = Arithmetic Mean

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 ...
0
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5answers
9k views

How can an object with zero acceleration move?

My physics text has a problem in which it is said that a person moves a block of wood in such a way so that the block moves at a constant velocity. The block, therefore, is in dynamic equilibrium and ...
3
votes
3answers
1k views

Physical Variables of Circular Motion

To me, the definitions of variables involved in circular motion are rather confusing (perhaps due to the lack of understanding on my part), hence the question. As I understand it, there are two ...
0
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3answers
927 views

Velocity is “Distance/Time” in a particular direction OR simply “Displacement/Time”?

Is velocity: Distance/Time in a particular direction, or simply Displacement/Time? Or both 1 and 2 is the same thing?
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1answer
1k views

How - The force of a 60 mph crash is not just twice as great as a 30 mph crash; it’s four times as great! [duplicate]

The DMV manual says that The faster you go, the less time you have to avoid a hazard or collision. The force of a 60 mph crash is not just twice as great as a 30 mph crash; it’s four ...
3
votes
2answers
809 views

A block on a wedge

The system is as follows - Friction exists only between the 2 blocks. I am trying to find out the accelerations of $m_1$ and $m_2$. Let $a_2$ be acceleration of $m_2$, and $a_x$ and $a_y$ be the ...
0
votes
1answer
108 views

Time taken for collision [closed]

We have three particles at the vertices of equilateral triangle of side $d$. At $t=0$ they start moving in such away that at all instant of time each of them has a speed $v$ towards adjacent one. We ...
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4answers
1k views

When we take time derivative of a function of time, then is the result another function of time, again?

(I'll try to explain my question by one known example), for example where the velocity is a function of time v(t) then its time derivative (which is acceleration: $a=\frac {dv}{dt}$) is another ...
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2answers
59 views

Is it incorrect to explain the direction of a coded vector quantity?

For example, let's say that in a linear physics problem, all the data are given to a certain direction, and coded positively for direction to the right. So +5m/s would be a velocity of 5m/s to the ...
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vote
2answers
343 views

Why can't some light ever reach earth? [duplicate]

Note: I'm a layman in physics. Excuse me if this question is a duplicate, I lack the knowledge in technical terms to find the answer to this by research (I've tried). Let's suppose there's a star ...
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votes
2answers
390 views

6 Story Building Swaying, Normal? [closed]

Preface: I'm currently sitting at my desk on a 5th floor in a South Florida office building, as I was earlier this morning when I felt the building sway slightly. It wasn't continuous and the ...