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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2answers
108 views
Non-zero higher time derivatives of position?
My mom told me to use speed control, which would allow the car to remain at constant speed. I told her that its impossible for a car to maintain constant speed, as slight changes in friction on the ...
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3answers
558 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 ...
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votes
2answers
317 views
Kinematics - concept question
A child tosses a ball directly upward. Its total time in the air is T. Its maximum height is H. What is its height after it has been in the air a time T/4? Neglect air resistance.
Ok so I know that ...
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1answer
122 views
I think I disprove this with kinematics, but energy says it is right
!
Here is my kinematics argument. For now I am only going to look at ball 2 and ball 3. Make note of the following data.
$|v_0| = 10m/s$, $y_0 = 10m$, $\theta_2^0 = 30^0$, $\theta_3^0 = -45^0, g = ...
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votes
2answers
315 views
How to calculate total distance and time a puck will move?
To simulate a puck's movement, I use the following model (please restrain from discussing the model, it makes the simulation look the way I want it to) and would like to know how to calculate the ...
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votes
2answers
109 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 ...
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votes
3answers
229 views
The required energy to accelerate a particle from one velocity to another
Say I have a charged molecule running along a linear evacuated tube (so no wind resistance). In the laboratory frame, we can measure that the particle is moving at some speed $v_1$. Provided that ...
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votes
1answer
252 views
Relationship between acceleration, velocity and position
I'm learning some applications for equation of motion. But I'm failing to relate velocity, acceleration and position.
If $v=\frac{dr}{dt}$ and $a=\frac{dv}{dt}$, why $a$ is $\frac{d^2r}{dt^2}$ ...
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3answers
252 views
Differential squared vs. differential of squared
Why it is said that
$$\frac{dx^2}{dt^2}=\upsilon^2$$
I can only understand the following one:
$$\left (\frac{dx}{dt} \right)^2=\upsilon^2$$
Edit:
Excerpt from Landau's Mechanics:
Execrpt from ...
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votes
2answers
330 views
How to compute drag coefficient given initial position, initial velocity and final resting position?
The equations I'm using are:
x = x + (DT * vx)
vx = vx * C
My DT is always 0.01 and the coefficient C (related to a linear ...
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votes
2answers
172 views
Question Concerning Position Of A Particle At Any Given Time
After years of procrastinating i've decided not to "move ahead" with physics without getting this ridiculously trivial question clear!*I know i had asked a similar question as silly and stupid as this ...
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2answers
781 views
What do I need to do to find the stopping time of a decelerating car? [closed]
The question is:
A car can be stopped from initial velocity 84 km/h to rest in 55 meters. Assuming constant acceleration, find the stopping time.
Sorry for my ignorance, but I need to review ...
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votes
2answers
3k views
Stopping Distance (frictionless)
Assuming I have a body travelling in space at a rate of 1000m/sec. Let's also assume my maximum deceleration speed is 10m/sec*sec. How can I calculate the minimum stopping distance of the body?
All ...
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votes
1answer
38 views
Relative Velocity problem
I was solving many problems on relative velocity and observed that when the question asks,
"what is the minimum time taken by the boat/man to cross the river.?"
so the solution says that he ...
0
votes
1answer
79 views
Reachable area of cannonball given fixed initial speed [closed]
The trajectory of a cannonball fired from the origin with initial speed $v_0$ at an angle $\theta$ is given by
$$y = x\tan\theta - \frac{g}{2v_0^2 \cos^2\theta}x^2.$$
For fixed $v_0$, at what angle ...
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votes
3answers
223 views
Deriving equations of motion using integration
Please refer to my school textbook pg48 (of the book, and not the pdf counter) here: http://ncertbooks.prashanthellina.com/class_11.Physics.PhysicsPartI/ch-3.pdf
My doubt is in this context: (right ...
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votes
2answers
82 views
Do you use the magnitude equation to get speed from an accelerometer?
A guy suggested to me that getting speed from an accelerometer required the use of this equation:
$\text{speed} = \sqrt{x^2 + y^2 + z^2}$
This does not make any sense to me, all that you would get ...
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votes
1answer
60 views
Is it necessary to know initial y velocity to solve this projectile motion problem?
A marble is launched horizontally off a 93.0-cm high table causing the marble to land on the floor 1.85 m from the base of the table.
a.) How long was the ball in the air?
b.) With what ...
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votes
2answers
167 views
Calculating vertical velocity component of a particle with mass, given the hit point of parabolic motion
Consider the following situation:
I have a particle with a given mass that at a given instant of time (let's say $t_{0}$) is placed at the system origin. The particle has a constant velocity ...
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votes
2answers
136 views
Energy Question
Carl throws 100 g of Bohrium-262 (Half life: 0.10 seconds, undergoes alpha decay) to Sukhdeep with a initial horizontal velocity of 20.0 m/s at an initial height of 2.00 m above the ground. What is ...
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2answers
88 views
Proof of $T=\sqrt{2y/a}$ in uniformaly accelerating object [closed]
Suppose that there is a object that does a y-axis-only free fall to ground. The initial distance from the ground is defined as $H$.
How does one prove that time the object takes to reach the ground ...
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votes
1answer
126 views
Proving $t=(1+\sqrt{1+2hg/v^2 } ) (v/g)$ for a thrown ball
If we throw a ball from the hight point $h$ from the earth, with initial velocity $v’$, how to prove that the time it takes the ball to reach the earth is given by:
...
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votes
3answers
354 views
Uniform Circular Motion
Why does the object not go inward, into the circle if the acceleration is inward? I think its because the velocity to outward? So they sort of cancel each other out? But if the speed is kept ...
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votes
1answer
217 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
votes
1answer
108 views
Do observers at different speeds perceive other speeds differently?
I was told that if a plane takes less time to travel from the China to US as opposed to the other direction due to rotation of the earth. I suspect this is incorrect however.
From this scenario I ...
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votes
2answers
280 views
Time and distance where velocity is a function of time
I'm creating a video game set in space in which spaceships travelling between places accelerate until they hit a maximum velocity. They then travel at that velocity until a time when they need to ...
0
votes
1answer
348 views
How do I determine a component of relative velocity?
At a particular instant, a stationary observer on the ground sees a package falling with speed v1 at an angle to the vertical. To a pilot flying horizontally at constant speed relative to the ...
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votes
2answers
340 views
Finding Distance an Object Travels Up an Incline After Launch
I've been doing a review for an introductory physics course final. I have a question on one problem though. Here is the problem:
A mass (M=2kg) is placed in front of a spring with k=900N/m,
...
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votes
2answers
260 views
Does acceleration at an angle to velocity change the direction?
During an interval of time, a tennis ball is moved so that the angle between the velocity and the acceleration of the ball is kept at a constant 120º. Which statement is true about the tennis ball ...
0
votes
2answers
662 views
Position in circular motion
Is it possible to determine the position of a particle undergoing circular motion, in x-y coordinates, at any given time and velocity?
I'm thinking it has something to do with $\pi$
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votes
1answer
146 views
Kinematics of scratching a rolling tire
Recently a "U" shaped scratch appeared on my car's front tire. It looks like someone rolled past a curb and scraped it. This has led me to the following problem:
Generate a plot (ideally polar) of a ...
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2answers
88 views
Given Angle, Initial Velocity, and Acceleration due to Gravity, plot parabolic trajectory for every “x”?
Given any Angle -> 0-90
Given any Initial Velocity -> 1-100
Given Acceleration due to Gravity -> 9.8
Plot every x,y coordinate (the parabolic trajectory) with cartesian coordinates and screen pixels ...
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votes
1answer
82 views
Kinematics with non constant acceleration
A particle experiences an acceleration described by
$$
a=kx^{-2}
$$
where x is the displacement from the origin and k is an arbitrary constant.
To what value does the velocity v of the particle ...
0
votes
1answer
70 views
Circular motion and centrifugal force
Assuming a race car drives around in a circle of radius r, center (0,0), linear velocity v, and ignoring centrifugal forces and friction I can calculate the position at any time, t.
Angular velocity
...
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votes
1answer
66 views
Kinematics question [closed]
An electric train accelerates uniformly from rest to a speed of 20m/s which it maintains until the brakes are applied. It is then brought to rest by a uniform retardation equal in magnitude to twice ...
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votes
2answers
121 views
How can I add an acceleration vector to a velocity with a different direction?
I am in my last year of high school and am struggling with some homework. I'm sorry if this question is incredibly stupid, but I simply can't find the answer in my notes.
If I have an object with a ...
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votes
2answers
143 views
Equation of motion for average acceleration
I am trying to solve the following:
A man of mass 83 kg jumps down to a concrete patio from a window ledge only 0.48 m above the ground. He neglects to bend his knees on landing, so that his ...
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votes
1answer
96 views
What's the difference between these two formulas and how are these called?
I just want to know the differences between these two formulas:
$h = h_0 + v_0 t ± \frac{1}{2} g t^2$
and
$y = y_0 + v_{0y} t + \frac{1}{2} g t^2$
Also, how are these called in English?
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votes
1answer
146 views
How do I find the magnitude and angle of the velocity?
I'm confused about the following problem.
A ball is shot from the ground into the air. At a height of $9.1\text{ m}$, its velocity is $v = (7.6\hat{\imath}+ 6.1\hat{\jmath})\text{m/s}$, with ...
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votes
5answers
254 views
How a spacecraft travelling near light speed avoid asteroids?
How would a spacecraft traveling near light speed avoid a (relatively dense group of) asteroids? Or suppose such spacecraft is designed, how would the physics work for steering it inside such a ...
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votes
2answers
195 views
What is the force of friction between two bodies given their masses and a force pulling them as a unit accross a surface?
Where a force of 200N pulls two blocks together(as one system) across a horizontal table top(µ=0.800)
$m_A$ = 5.00kg, $m_B$ = 10.0kg
Find the acceleration of the system.
Find f$_k$ between B and A
...
0
votes
1answer
138 views
Two Different Sorts of Inertia: Inertial Mass and Moment of Inertia
There are two different sorts of inertia: inertial mass and moment of inertia.
I am currently reading about moment of inertia. Now, I know inertia is an important concept; with it, we can determine ...
0
votes
2answers
969 views
Acceleration/tension of object. 1 on horizontal surface one hanging
A 5.00-kg object placed on a frictionless, horizontal
table is connected to a cable that passes over a pulley and
then is fastened to a hanging 9.00-kg object, as in Figure. Find
the ...
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votes
2answers
835 views
How do you calculate angle of projection?
At what angle the projectile should throw with initial velocity v in order to reach distance d? discard the air resistance, only gravitation acts. So far I got the equations for horizontal and ...
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votes
1answer
130 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.
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votes
2answers
255 views
Closest model for relationship between velocity and distance
Which is the model that best shows the relationship between velocity and distance:
$v \propto d$
$v \propto d^2$
$v^2 \propto d$
$v^2 \propto d^2$
What I think is from:
$$v=at \Rightarrow ...
0
votes
2answers
264 views
Maximum velocity allowed for motion profile with constant jerk
I´m trying to calculate what the maximum allowed velocity for a mechanical axis traveling towards a stop. The maximum velocity must be a secure speed so the axis have is able to stop in time.
I have:
...
0
votes
2answers
94 views
Really basic mechanics and Galilean Relativity question
Consider two solid objects: A and B.
System 1:
A <----- B
10m/s
System 2:
A -----> B
10m/s
...
0
votes
2answers
382 views
Does an airplane's speed include the speed of the Earth?
After take off, does airplane's speed include Earth's movement/speed? Do airplanes turn with Earth movement/rotation?
0
votes
1answer
134 views
Looking for a way to simplify a physics formula [closed]
I have the following physics formula:
$$d = \frac{1}{2} at^2$$
where d is equal to half (at) squared
where:
d is distance
a is acceleration
t is time
I need to simplify this to get the ...
