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.
3
votes
1answer
186 views
So what is happening in this angular kinematics equation?
The wheel of a car has a radius of 20 cm. It initially rotates at 120
rpm. In the next minute it makes 90 revolutions. What is the angular
acceleration?
So the answer is solved by using one ...
3
votes
3answers
3k 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 ...
1
vote
3answers
4k views
Find radius of curvature, given a velocity vector and acceleration magnitude?
The particle P moves along a space curve. At one instant it has velocity $v = (4i-2j-k)$ $m/s$. The magnitude of the acceleration is 8 $m/s^2$. The angle between the acceleration and the velocity ...
2
votes
1answer
393 views
Circular equation of motion
I'm reading an article which describes a generation of artificial AKG signal. The article states that they use the following equation of motion:
$ \left \lbrace \begin{array} {ccc} \dot x &=& ...
1
vote
2answers
220 views
Doubt concerning centripetal acceleration
What is the centripetal acceleration and angular velocity of a child located 8.2 m
the center of a carousel? The speed (size of the tangential velocity) of the child is
2.1 m / s
A train moves in a ...
1
vote
1answer
1k views
Ascent rate and size of balloon
I am part of a school project, Project Stratos to send a balloon to the edge of space (the closer side :P) and was wondering how you would work out the accent rate of a large balloon (roughly 1m^3 of ...
1
vote
2answers
220 views
Running: Determine how much more energy is needed per extra kilogram of weight
(I recently asked this on maths but was directed here)
I have recently become a runner and having a keen interest in kinematics I'm very interested in the maths/physics of my running.
Can someone ...
0
votes
2answers
131 views
In a 2D problem with a thrown object, why is the acceleration along the x-axis equal to 0?
I'm starting Physics, and I don't understand why the acceleration along the x-axis is zero for an object thrown near the surface of the Earth. This may be problem specific, but I wouldn't know since I ...
0
votes
2answers
458 views
Can someone explain the physics of a standing jump?
I would like to use something like a kinematic equation to know where the person will be in the jump at a given time. However since I think acceleration is not constant because of the jump force it ...
3
votes
2answers
971 views
Formulas for ball rolling in a bowl?
I'm developing a program where I've a ball/sphere rolling in a bowl from the side at top, till the center at bottom, and I'm trying to get the formulas for:
The rotation angle and the position of ...
0
votes
2answers
696 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 $\pi$
2
votes
1answer
132 views
Is it possible to rotate an angle on perfectly smooth ice?
You must start and end with the same pose.
Prove it if you think you can't.
5
votes
2answers
6k 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 ...
-1
votes
3answers
276 views
Help getting the distance an object has moved
What is a distance an object went through at the speed of 14hm/min for 6 hours?
I am having problems with conversions.
First, I tried passing 14hm/min to m/s. I did it alright. But now I am unsure. ...
7
votes
3answers
416 views
What's my weight when jumping on a bicycle from a higher to a lower ground?
Before I start defining the situation and asking a question, I'd like to make a few things clear:
this is not a homework, merely a matter of personal interest and enthusiasm
I am neither a ...
0
votes
3answers
245 views
Deccelerate and Accelerate to achieve timed journey
I have a vehicle traveling at initial speed $100\:\mathrm{m/s}$.
Expected destination speed is also $100\:\mathrm{m/s}$.
Maximum deceleration is $3$.
Maximum acceleration is $10$.
Distance to the ...
2
votes
4answers
3k views
How to calculate displacement of an object
I am having a little bit of trouble with this following problem -
Suppose a particle has initial velocity and is moving with a constant acceleration. After t seconds its velocity is v. What will its ...
2
votes
2answers
316 views
Is the speed of a person falling down different if doing a forward somersault during the fall?
Let's imagine this in an situation where a person jumps down from a smaller building, a garage for example. The exact numbers aren't really important here, since I'm not aiming for an exact answer, ...
4
votes
2answers
815 views
Rigid body dynamics joints
I can't seem to find any info on connected rigid bodies by a joint. Can someone explain the basics to me? I'm trying to do a little research to find out how feasible it would be to implement 3d ...
6
votes
2answers
801 views
Physics of simple collisions
I'm building a physics simulator for a graphics course, and so far I have it implementing gravitational and Coulomb forces. I want to add collisions next, but I'm not exactly sure how to go about ...
1
vote
7answers
3k views
I need help with finding distance traveled
How do I find the distance traveled of an object if the speed is not constant?
1
vote
0answers
239 views
Kinematics textbook illustration
I have trouble interpreting this illustration. I see why r (position) and a (acceleration) are the way they are, but what happened to v? Why is it smaller than its coordinates? Is this another error ...
1
vote
2answers
218 views
Simple kinematics excercise, throwing something upwards
I am trying to solve this simple excercise:
Question
You throw a small coin upwards with $4 \frac{m}{s}$ . How much time does it need to reach the height of $0.5 m$ ? Why do we get two results?
...
2
votes
14answers
4k views
List of good classical physics books
What are some good books for learning the concepts of Kinematics, Newton laws, 2D Motion of Object etc.?
1
vote
2answers
796 views
Projectiles problem solving
I've only learned about to use kinematics equation when solving projectile problems but today i came across the following equations. where does they come from?
Distance travelled
Time of flight
...
0
votes
2answers
4k 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 ...
1
vote
1answer
1k views
Solving straight-line motion question for time
I apologise in advance if this question doesn't appeal to the advanced questions being asked in this Physics forum, but I'm a great fan of the Stack Exchange software and would trust the answers ...
0
votes
1answer
150 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 ...
1
vote
1answer
212 views
Is there a theory about kinetic energy “particles”? [closed]
We have a model of electricity which says electrons flow from one place to another. We have a model of optics which says that photons go from one place to another. As I understand, there is currently ...
3
votes
2answers
710 views
Is there a 2D generalization of the coefficient of restitution?
The coefficient of restitution characterizes a collision in one dimension by relating the initial and final speeds of the particles involved,
$$C_R = -\frac{v_{2f} - v_{1f}}{v_{2i} - v_{1i}}$$
In a ...
15
votes
10answers
13k views
What is the difference between “kinematics” and “dynamics”?
I have noticed that authors in the literature sometimes divide characteristics of some phenomenon into "kinematics" and "dynamics".
I first encountered this in Jackson's E&M book, where, in ...
37
votes
14answers
7k views
Why does kinetic energy increase quadratically, not linearly, with speed?
As Wikipedia says:
[...] the kinetic energy of a non-rotating object of mass $m$ traveling at a speed $v$ is $mv^2/2$.
Why does this not increase linearly with speed? Why does it take so much ...
2
votes
3answers
704 views
Distance travelled in free-fall
When an object is in free fall, we have:
$a(t) = g - \frac{c}{m}v(t)^2$
where $g$ is acceleration due to gravity, $m$ is the mass of the object, and $c$ is the coefficient of air resistance.
How ...
6
votes
5answers
9k views
How to calculate average speed
I recently encountered a puzzle where a person drove 120 miles at 40mph, then drove back the same 120 miles at 60mph. The average of the speeds is (40mph+60mph)/2 = 50mph, so the total trip time ...
