The velocity tag has no wiki summary.
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0answers
86 views
Physics about plane take off simple find the acceleration problem [closed]
This was on my test, but I kinda botched it I think.
I was trying to use
V^2f = Vo^2 + 2a(delta x)
A plane must reach 226km/h to take off. Runway is 2000m. What's minimum acceleration needed? ...
1
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0answers
42 views
Truck driven from a small motor that can carry a heavy load, yet can travel fast.
I am building a truck from trash as materials. I have one small motor and a a few small gears, but no other engineered materials are allowed. The truck must carry a load for a distance of 3m. The ...
1
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2answers
94 views
Escape Velocity question
I would like some help in understanding the derivation of the formula for escape velocity.
Why does $t$ approach infinity? And why is $v(t)$ approaching zero?
I know that $r(t)$ is infinite because ...
1
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1answer
142 views
Projectile motion problem with upward acceleration and horizontal velocity [closed]
An electron in a cathode-ray tube is traveling horizontally at 2.10×10^9 cm/s when deflection plates give it an upward acceleration of 5.30×10^17 cm/s^2 .
B.) What is its vertical displacement during ...
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0answers
58 views
Bernoulli's Principle [closed]
A clear plastic tube with a diameter of 12cm and 110cm high is filled to the top with mercury. (density = 13.6 kg/m^3). There are three holes, all with a radius of 2 millimeters located 15cm from the ...
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6answers
611 views
When driving uphill why can't I reach a velocity that I would have been able to maintain if I started with it?
Consider these two situations when driving on a long straight road uphill:
Starting at a high velocity $v_h$, which the car is able to maintain.
Starting at a lower velocity $v_l$, and then trying ...
0
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1answer
81 views
Vertical velocity to reach a certain point given a flat horizontal velocity? [closed]
Suppose I have two points such as $a(4,6,9)$ and $b(32,5,12)$.
If I have a flat velocity pointing $a$ to $b (b - a)$ which has an arbitrarily defined magnitude. Given gravity $g$,how can I calculate ...
2
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3answers
195 views
If you could reverse gravity, what velocity would you achieve on leaving Earth?
If you could reverse gravity, to make it repulsive instead of attractive, what velocity would you achieve on leaving Earth? A simple question really, but I have completely forgot how to calculate ...
6
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4answers
479 views
How to brake 'beautifully'?
Sometimes when I'm driving my car, I play a "game" against myself in which I try to minimize the deceleration felt by passengers (including myself) while still braking in a reasonable short space. I ...
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2answers
77 views
If airplanes' highest speed depends directly on the air it is moving through and not the ground,
If airplanes' highest speed depends directly on the air it is moving through and not the ground, does it mean we can build a time machine if only the air moves near the speed of light?
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8answers
517 views
Can you completely explain acceleration to me?
I understand what acceleration is, and I know the formula, and I understand it's a vector.
I just don't understand how the equation works exactly. I'm kind of picky, I know, but bear with me.
...
2
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1answer
179 views
Connecting 4-velocity to equation for adding velocities
Is there a way to connect 4-velocity to equations for adding speeds? I know 4-velocity $U^\mu$ is derived like this:
\begin{equation}
\begin{split}
P^\mu &= m U^\mu \Longrightarrow
U^\mu = ...
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0answers
147 views
What is the pressure in a vertical pipe that has moving fluid through it?
I have a system like this
When the valve is closed, pressure along any point along the thin tube may be found thru pgh. 1. What about when the valve is opened? 2. Does the top of the jar need to be ...
1
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1answer
185 views
Velocity of real gas molecules?
It is known that the velocity of ideal gas molecules can be computed using Maxwell-Boltzmann law of distribution of molecular velocities, with average velocity given as:
...
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5answers
487 views
How can kinetic energy be proportional to the square of velocity, when velocity is relative?
Let's start with kinetic energy (from los Wikipedias)
The kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a ...
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1answer
356 views
Relative Velocity and Momentum
The question is, "A $45.5~kg$ girl is standing on a $140~kg$ plank. Both originally at rest on a frozen lake that constitutes a friction-less, flat surface. The girl begins to walk along the plank at ...
1
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2answers
612 views
What does the velocity of a wave mean?
I know that the velocity of a wave is given by $v=\lambda f$ but what does this velocity represent in the physical sense. For instance, if I am told a car moves at a velocity of 5 $m/s$ I know that ...
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0answers
199 views
Is there an easy derivation of relativistic velocities addition and relativistic doppler shift?
Is there an easy derivation of relativistic velocities addition and relativistic doppler shift?
I'm looking for some easy derivation of the above. Like this ...
1
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1answer
130 views
How much runway does the space shuttle need to land?
A textbook question proposes the following scenario:
NASA needs to plan emergency landing sites for the Space Shuttle (RIP). There are a number of things to consider. The shuttle touches down no ...
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2answers
117 views
Negative sign of acceleration [closed]
This is the problem from our Physics textbook :
A player throws a ball upwards with an initial speed of 29.4 m s–1.
(a) Choose the x = 0 m and t = 0 s to be the location and time of the ball at ...
2
votes
1answer
282 views
How accelerometers sense constant velocity movements
There is something I don't understand about accelerometers. I know it's possible to make an Inertial Measurement Unit (IMU) by using "three" accelerometers. So with that, I could calculate the $x$, ...
3
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1answer
319 views
How do I find the initial velocity in this problem?
An X-ray tube gives electrons constant acceleration over a distance of $20\text{ cm}$. If their final speed is $2.0\times 10^7\text{ m/s}$, what are the electrons' acceleration?
I know this ...
2
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1answer
250 views
From how deep into space can a human “skydive” back to earth? [duplicate]
Possible Duplicate:
From how high could have Felix Baumgartner jumped without disintegrating like a shooting star?
If a human can skydive from an altitude of 24 miles (39 km), and a ...
11
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2answers
754 views
How fast would a spaceship have to go to reach Alpha Centauri within a person's lifetime?
Given the recent news about the discovery of an "Earthlike" planet orbiting Alpha Centauri (our nearest stellar neighbour) it got me wondering just how fast would spaceship have to travel to be able ...
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1answer
260 views
How does Baumgartner slow his velocity so that the parachute can open up?
How does Baumgartner slow his velocity so that the parachute can open up?
What is Baumgartner's speed just before his parachute opens?
What causes his speed to slow down just before the chute opens?
...
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1answer
2k views
From how high could have Felix Baumgartner jumped without disintegrating like a shooting star?
Today Felix Baumgartner jumped from 39 kilometres high and reached the earth safely.
Just considering friction, from how high can a human jump?
I expect that from a certain height, he would have ...
1
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0answers
71 views
What direction a flag on an object moving in the wind shows?
"The flag of a ship that is moving northward with 10 km/h, points exactly southwestward. The windsock at the lighthouse points under 30 relative to the western direction southward. Calculate the ...
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3answers
604 views
Calculating car's acceleration from change in angle of hanging object?
The question essentially is based on a situation like this-
A car has a small object hung from the cieling on a string (apparently at an angle of 0 degrees to the ceiling).
The car is accelerating ...
2
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4answers
999 views
Physics behind Wheel Slipping
Lets say that I'm in a car and I apply full acceleration suddenly. Now, the wheels would slip and hence the car doesn't displace much.
But If I start with some constant acceleration, slipping doesn't ...
0
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0answers
274 views
Magnitude of average velocity [closed]
A particle is at the position with Cartesian components $(5.0 m, 4.0 m)$ and $5.0 s$ later it is at the position with components $(8.0 m, 0.0 m)$. What is the magnitude of its average velocity?
I ...
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0answers
76 views
Jumping on a landing pad [closed]
I'm trying to make a character jump on a landing pad who stays above him. Here is the formula I've used (everything is pretty much self-explainable, maybe except character_MaxForce that is the total ...
1
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3answers
263 views
when an object moves downward, is its height negative?
the question is:
A ball is thrown directly downward with an initial speed of 8.00m/s from a height of 30.0m. After what time interval does it strike the ground.
so i went through the problem and ...
2
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0answers
45 views
Reaching the speed of light, rockets [duplicate]
Possible Duplicate:
Double light speed
Someting almost faster than light traveling on something else almost faster than light
Well I've been wondering quite a long time about this ...
2
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0answers
132 views
2D Car Physics including Throttle
For a simulation for testing on automatic cruise control, I came across the equation:
$$
v_{n+1} = (1 - k_1 / m) v_n + (1 - k_b) \begin{pmatrix}
T_n \\
θ_n \\
\end{pmatrix}
$$
where:
$T$ = ...
2
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2answers
259 views
Lever Mechanics - How to formulate an ideal lever launch
Let's say I have a simple lever as shown below, and the lever is massless and the pivot is frictionless and there is no air resistance. I'm thinking the cradle for the projectile would have to have a ...
0
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1answer
134 views
Power, Force Velocity
In any case, if the force and power is constant , does velocity also need to be constant? If no, can you tell me a case.
Further can this be extended for non-rigid bodies.
3
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2answers
633 views
Group Velocity and Phase Velocity of Matter Wave?
In quantum mechanics, what is the difference between group velocity and phase velocity of matter wave? How can it also be that phase velocity of matter wave always exceeds the speed of light?
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4answers
1k views
What is the general formula for a trebuchet?
What I'm really looking for is a formula for a trebuchet that I can input the desired initial velocity after launch and mass of the object, and from that figure out how long the long arm, short arm, ...
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2answers
225 views
Calculating two particle position and velocity with each other?
I've calculated the displacements and average velocities of both particles.
$A$ average velocity $= 1.1180m/s$ displacement is $11.1803m$.
$B$ average velocity $= 0m/s$ displacement is $0m$.
...
0
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0answers
487 views
Create general equation of racing cars with head start [closed]
Cars A and B are racing each other along the same straight road in the following manner: Car A has a head start and is a distance $d_A$ beyond the starting line at $t=0$. The starting line is at ...
1
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2answers
535 views
Difference between deltaV and specific impulse
When reading any literature regarding space propulsion, I keep getting about these terms deltaV and ISP or specific impulse. I know specific impulse is supposed to be the velocity the propellant mass ...
1
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1answer
328 views
Calculating velocities using Reference frames
Suppose an object A is traveling at a velocity of 100 m/s, and another object B is traveling at 105 m/s. With both the objects traveling through the same direction, taking A as a reference frame, the ...
3
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2answers
697 views
How can an object's instantaneous speed be zero and it's instantaneous acceleration be nonzero?
I'm studying for my upcoming physics course and ran across this concept - I'd love an explanation.
-1
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1answer
128 views
What is the quantity in physics that is advanced from speed? [closed]
What is the quantity in physics that is advance from speed?
i know one is velocity, one is speed, one is acceleration.
0
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1answer
232 views
End position of movement factoring in deceleration
Ok I am hoping to apply this answer to a piece of software, but it uses physics to work out the result so I require some help in that department.
I will attempt to explain this the best I can.
I ...
0
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1answer
64 views
What is the shortest run needed for a “dropped skateboard” rider to reach 160 mph?
I just saw a great clip on the fastest skateboarder to date. He wants to reach 160 mph from a dropped board, but says his speed is limited by the roads currently available. What is the shortest run ...
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3answers
1k views
What is the physical meaning of diffusion coefficient?
In Fick's first law, the diffusion coefficient is velocity, but I do not understand the two-dimensional concept of this velocity. Imagine that solutes are diffusing from one side of a tube to another ...
1
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1answer
119 views
Determining Orbital Velocity
Is there any way to determine the orbital velocity of a point around another stationary point, if I don't know the mass of either of the points but know the force that gravity exerts and the distance ...
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2answers
2k views
Flow of liquid among branches
If water is flowing through big pipe is branched into 4 branches of small pipe. Lets say the flow is around 4 m/sec.
I have the following questions:
What will be the flow rate in each of the ...
-1
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1answer
211 views
Hit a moving target [closed]
There is an object moving from $(X_1,Y_1)$ to $(X_2,Y_2)$ with speed of $V$. there is a third object in in $(X_3,Y_3)$.
now I want to hit the first object with the second one. and imagine that the ...
