The rate of change of velocity of a body per unit of time.
3
votes
1answer
607 views
Is acceleration due to gravity constant?
I was taught in school that acceleration due to gravity is constant. But recently, when I checked Physics textbook, I noted that
$$F = \dfrac{G \cdot m_1 \cdot m_2}{r^2} $$
So, as the body falls ...
0
votes
1answer
58 views
Vehicle acceleration
What I'm essentially doing is Kalman Filter. If anyone is familiar with (but it doesn't really matter in this case). Consider the following formulas:
...
-1
votes
4answers
203 views
How to send a spacecraft to the moon without any acceleration
I have two (maybe equal) question
1- Is this possible to send a spacecraft to the moon without any acceleration(Constant speed)?
2-Is this possible to throw a ball on the top of tree without any ...
1
vote
2answers
274 views
Special Relativity: What differential equation describes an accelerated object from a non-inertial reference frame?
I am looking for a set of differential equations (to be solved numerically for an educational program) that would describe the position and apparent time of an accelerated clock relative to a ...
5
votes
2answers
285 views
relativistic acceleration equation
A Starship is going to accelerate from 0 to some final four-velocity, but it cannot accelerate faster than $g_M$, otherwise it will crush the astronauts.
what is the appropiate equation to constraint ...
3
votes
2answers
616 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.
0
votes
4answers
543 views
Questions from elevator ride
I like to play inside the lift (elevator). For instance, there are bars attached at the side of the lift, and I like to hold my body up using my two hands on the bar. I realised that I actually feel ...
0
votes
2answers
164 views
Why equivalence principle is principle and not law?
We can prove that the inertial mass and the gravitational mass should be the same (equivalence principle) from the $f=mg=ma$ then $g=a$, so we have equivalence law! But why we said equivalence ...
1
vote
1answer
270 views
Suvat equations in reverse direction
This might be a basic question, but please help me out.
I have an object traveling in the positive direction with a velocity $v$
and I wish to apply a constant acceleration so that the final velocity ...
0
votes
1answer
267 views
Acceleration of a car required to reach point B with velocity D from point A with velocity C in time T
How do I get the acceleration of a car required to reach point B with velocity D from point A with velocity C in time T?
I understand the acceleration is not constant but how can I calculate the ...
2
votes
5answers
977 views
Why Gravity attracts all objects with the same speed?
Why Gravity attracts all objects with the same speed? Is this question was solved? What is the exact answer?
0
votes
1answer
2k views
Finding deceleration and velocity using distance and time
A car is moving down a street with no brakes or gas. The car is slowing due to wind resistance and the effect of friction. The road is flat and straight. The only data I have are timings taken at 100m ...
1
vote
0answers
89 views
maximum distance between accelerating objects started at different times [closed]
Let there be two objects that have zero relative velocity with respect to each other in an inertial frame. If they both undergo identical accelerations, but one starts the acceleration at t = T1 and ...
0
votes
0answers
73 views
Does human body parts like hand or leg move with uniform acceleration?
So is this true. I mean does a movement by hand or leg make uniform or constant acceleration?
0
votes
2answers
281 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 ...
-1
votes
1answer
124 views
Does light photons have jerk
While searching in web regarding whether rate of change of acceleration is possible or not; i came across the concept of jerk.I want to know whether light which can be accelerated can also have jerk ...
0
votes
3answers
363 views
Finding instantaneous speed in MPH given acceleration, RPM and gear ratio
I am still trying to figure out how to (semi) accurately model instantaneous speed after having found acceleration. I have found that at higher RPMs, the resultant acceleration will be lower. I was ...
2
votes
2answers
846 views
Finding acceleration for a car after finding torque
I am trying to calculate the acceleration of a vehicle after finding the torque $\tau$. Assuming my Horse Power is 130 and my RPM is 1000, I calculated torque as:
$$\tau = \frac{130 \times ...
0
votes
3answers
197 views
How to determine an exponential acceleration curve?
I've always been not so bad in mathematics, but I'm terribly bad at physics. For me, abstract concept are totally understandable, but when it come to reality, I'm lost !
So, for my job, I need to ...
11
votes
4answers
376 views
Is there an easy way to show that $x^2-t^2=1/g^2$ for a (relativistic) body undergoing acceleration g?
A professor asked me about the (c=1) equation:
$$x^2 - t^2 = 1/g^2$$
which I used in a paper. Or with $c$:
$$x^2 - (ct)^2 = c^4/g^2.$$
I told him that it was the exact equation of motion for a ...
0
votes
2answers
272 views
When we throw an object in the presence of gravitational attraction is the mass of the object proportional to the time of fall or not?
I was confused when i saw two object of different masses (A and B)falling from the same height(h) but both of them strikes the ground at same time. Is this possible, that masses of the objects are ...
1
vote
1answer
535 views
What is the difference between an accelerometer and an inclinometer?
When looking through papers for a controls project I found one that seemed to be referencing the fusing of sensor data from an inclinometer and an accelerometer.
I always had thought that it was ...
0
votes
3answers
940 views
Why is force described as rate of change of momentum?
momentum = mass * velocity
Differentiating both sides leads to
force = mass * acceleration
since the mass doesn't participate in the differentiation as it is constant.
Is this a sound ...
0
votes
0answers
215 views
How to decide velocity profile for two stepper motor in robot driving
A robot has 2 parallel driving wheel. I don't know the friction of the ground surface. However, I can set the acceleration, starting velocity, ending velocity. The velocity profile has to be ...
0
votes
2answers
2k views
Why does a parachute decrease terminal velocity?
Terminal Velocity depends on two things- surface area and speed. These are inversely proportionate.
If both these variables affect terminal velocity, why do parachutes slow you down? Initially you ...
4
votes
3answers
421 views
Infinite acceleration?
Why is acceleration regulated by mass? In a frictionless environment, why doesn't an object move at infinite acceleration if force is applied on it?
Force causes movement, so unless there is an ...
1
vote
1answer
140 views
Accelerating elevator?
If your in an elevator accelerating downwards faster than gravity, would you be pushed up to the ceiling? Since gravity cannot match the acceleration of the elevator, you're wouldn't be able to move ...
3
votes
1answer
141 views
A practical deceleration question
My friend is a U.S. Army paratrooper. Today, through an unfortunate series of events, he was jerked out of a C-17 traveling at 160 knots by his reserve parachute. First-hand accounts describe it as he ...
0
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 ...
2
votes
4answers
149 views
Why is the time taken for something to fall proprtional to acceleration due to gravity?
This is a continuation of this question.
I saw in a piece of writing (that I no longer seem to be able to aquire) on dimensional analysis that:
$$t \propto h^\frac{1}{2} g^\frac{-1}{2}.$$
How can ...
1
vote
2answers
316 views
At what point does a projectile leave a slingshot?
Assuming a frictionless / "perfect" environment, and given a ball held in an elastic sling (like a hand-held catapult) where the pocket is lighter than the projectile itself, what is the point at ...
0
votes
1answer
160 views
Deceleration of Vehicle off pavement
How would I calculate the deceleration of a vehicle (ATV), wheels locked, on dirt? How long would it take to halt? How fast is it decelerating?
I used this calculator, but it seems incorrect for a ...
4
votes
3answers
769 views
Is acceleration relative?
A while back in my Dynamics & Relativity lectures my lecturer mentioned that an object need not be accelerating relative to anything - he said it makes sense for an object to just be accelerating. ...
1
vote
1answer
608 views
How to find acceleration given position and velocity?
Sorry for this very simple question but I am still very new to the laws of motion.
I am dealing with 2-dimensional vectors in my programming environment and I'm following these slides to learn about ...
1
vote
1answer
776 views
Can we determine the force an object exerts by its mass and acceleration?
I understand that the objects acceleration is determined by the force exerted on it, and that the force exerted on it is determined by its acceleration.
But, does an object's (named A) acceleration ...
8
votes
3answers
364 views
Whether $m$ in $E=mc^{2}$ and $F=ma$ are both relativistic mass?
I know that $m$ in $E=mc^{2}$ is the relativistic mass, but can $m$ in $F=ma$ can also be relativistic? If the answer is yes, then can you tell me whether this equation is valid $E=\frac{F}{a}c^{2}$? ...
2
votes
3answers
587 views
Example in the book: A simple accelerometer
A simple accelerometer
You tape one end of a piece of string to the ceiling light of your car and hang a key with mass m to the other end (Figure 5.7). A protractor taped to the light allows you ...
3
votes
2answers
221 views
A simple thought experiment about traversable wormholes
Let's say I have a tube, of large radius (about 5 - 7 meters in diameter), with traversable wormholes at the ends. The wormholes are arranged as such that if something falls inside one hole from ...
2
votes
1answer
212 views
Thought experiment about acceleration
Case 1: two people wake up in spaceships accelerating at 1g. They can measure or observe anything inside the room but not outside. They couldn't determine if they were on a spaceship or on earth. ...
7
votes
2answers
809 views
Relativistic centripetal force
The thought randomly occurred to me that a circular particle accelerator would have to exert a lot of force in order to maintain the curvature of the trajectory. Many accelerators move particles at ...
1
vote
2answers
74 views
Acceleration: Value Disparity?
If we consider a ball moving at an acceleration of $5ms^{-2}$, over a time of 4 seconds, the distance covered by the ball in the first second is $5m$. In the 2nd second will $5 + 5 = 10m$. In the ...
2
votes
3answers
784 views
What is the velocity area method for estimating the flow of water?
Can anyone explain to me what the Velocity Area method for measuring river or water flow is?
My guess is that the product of the cross sectional area and the velocity of water flowing in a pipe is ...
1
vote
6answers
1k views
Does light have acceleration?
Light travels with the largest speed in our universe. Does light have acceleration?
3
votes
2answers
506 views
Does a moving escalator make it easier to walk up the steps?
I was discussing with my colleagues why it feels easier to walk up an escalator when it is moving. My natural assumption was that the movement of the escalator imparts some extra acceleration on the ...
0
votes
2answers
1k views
What is the force exerted on a body that doesn't move?
If I push against a brick wall I'm exerting a force against the brick wall the the brick wall will exert the same force against me. These will cancel each other out and neither myself or the wall will ...
3
votes
1answer
103 views
Why is cosmological acceleration expressed in terms of an energy density?
In the articles that I have (tried to) read, acceleration ends up being expressed as a dimensionless constant (omega-lambda) or else occasionally in terms of a "dark" energy density. Presumably one ...
2
votes
1answer
522 views
Do all planets rotate around the sun with the same acceleration?
I have this question in mind. suppose if by any chance, all planet around sun stopped rotating. then as per formula F= M * A. all planet should fall with same acceleration towards sun and ultimately ...
2
votes
5answers
437 views
Why doesn't an electron accelerate in a circuit?
Why don't electrons accelerate when a voltage is applied between two points in in a circuit? All the textbooks I've referred conveyed the meaning that when an electron traveled from negative potential ...
2
votes
2answers
591 views
How much effect does the mass of a bicycle tire have on acceleration?
There are claims often made that, eg, "An ounce of weight at the rims is like adding 7 ounces of frame weight." This is "common knowledge", but a few of us are skeptical, and our crude attempts at ...
0
votes
3answers
654 views
Who is right? Force exerted on a body. Me or my friend?
Three masses $m_1 = 3\text{ kg}$, $m_2 = 9\text{ kg}$ and $m_3 = 6\text{ kg}$ hang from three identical springs in a motionless elevator. The elevator is moving downward with a velocity of $v = ...
