0
votes
2answers
46 views
Momentum, Impulse and Newton's Second Law of Motion
Newton formulated his Second Law as such:
$$\sum{\vec{F}} = \frac{\delta \vec{p}}{\delta t}$$
and of course, $\vec{p} = m \vec{v}$.
Why is it that if the net force $\sum \vec{F}$ is constant (which ...
5
votes
0answers
76 views
+50
How multiple objects in contact are resolved in an inelastic collision, when edge normals don't “line up”
In a case I understand, let's say I have an object A moving at velocity V toward 3 objects in contact B, C, and D:
The momentum of A is the mass of A times its velocity. To figure out how the ...
0
votes
2answers
44 views
Simple conservation of momentum and frame of reference problem
I'm making a very simple physics engine based on momentum, and I'm solving what response to use for a collision from each involved object's frame of reference. However, something about how I'm ...
3
votes
1answer
70 views
Conservation of momentum in collision of two bodies
Suppose we have some ramp on wheels of mass $M$, standing on a
frictionless surface. A cart of mass $m$ moves with a certain velocity
$v$ towards the ramp. The cart moves up the ramp ...
3
votes
2answers
157 views
Firing machine question
Suppose we have a firing machine on a frictionless surface at point $x=0$. It fires a bullet of mass $m$ every $T$ seconds. Each bullet has the same constant velocity $v_0$. There's a body of mass ...
3
votes
2answers
58 views
Two-body problem questions
I am self studying the two body problem and I'm stuck on the following:
I have given $$\ddot{\vec{x}}_1= - G m_2 \frac{\vec{x}_1-\vec{x}_2}{|\vec{x}_1-\vec{x}_2|^3}$$ and $$\ddot{\vec{x}}_2= - G ...
0
votes
5answers
173 views
Why is momentum conserved (or rather what makes an object carry on moving infinitely)?
I know this is an incredibly simple question, but I am trying to find a very simple explanation to this other than the simple logic that energy is conserved when two items impact and bounce off each ...
0
votes
1answer
72 views
Newton's second law?
$F=ma$. A car strikes a wall at 60 mph. Its acceleration is zero at the time. The force of the car against the wall or vice versa is? To look at the car the force is not zero. Please explain.
3
votes
1answer
142 views
Why is momentum conserved when a ball hits a vertical wall?
Almost in every book on physics, there's an example of conservation of momentum when the ball that is moving horizontally in the air, hits some massive wall. They claim that the return speed of the ...
3
votes
2answers
72 views
Conservation of Linear Momentum at the point of collision
This is a pretty basic conceptual question about the conservation of linear momentum.
Consider an isolated system of 2 fixed-mass particles of masses $m_1$ and $m_2$ moving toward each other with ...
1
vote
2answers
48 views
effect of vertical collision on kinetic friction and subsequent change in horizontal velocity
Suppose somehow a block of mass $m$ is moving on ground, and the coefficient of kinetic friction between the block and the block is $\mu_k$. If I drop a tennis ball(of same mass) on it from a ...
2
votes
2answers
112 views
Movement of man and ladder and their center of mass
Suppose there is a massless frictionless pulley.
A rope over it carries a mass $M$ and on other side carries a ladder of mass $(M-m)$ and a man on that ladder, of mass $m$. Now the man starts ...
1
vote
1answer
122 views
Inelastic collision and impulse
Suppose I have some cart moving horizontally in a straight line and with a constant velocity, and there is no friction between the surface and the cart. Now, I throw a plasticine on the cart at some ...
1
vote
4answers
201 views
Bat hitting a ball
When a bat hits a ball, consider two cases:
1) The batsman goes for a defense, and stonewalls it, to reduce its speed.
2) the batsman goes for a shot, e.g. a home-run, etc.
in which case will the ...
1
vote
1answer
70 views
Shooting a bullet at a system of blocks [closed]
So, I made this question up myself.... and I'm curious about the answer. It requires only secondary-school-level knowledge of physics:
You have a surface (ground) with a certain coefficient of ...
2
votes
2answers
102 views
A thought on definition of momentum
Well, this is a simple, basic and I think even silly doubt. The first time I saw the definition of momentum as $p = mv$ I started to think why this is a good definition. So I've read the beginning of ...
0
votes
1answer
159 views
Calculating a 2D collision between two perfectly circular disks
Assume I have two disks, $p_1$ and $p_2$, of radius $r$, with their own velocities (preferably in $(x,y)$ form, but $(m, \theta)$ works too) and masses (unit-less, but same unit) collide in two ...
0
votes
1answer
140 views
What happens if object is thrown in empty space?
If I throw a object in empty space, I apply a force to throw that.
Then it gains some acceleration and it's speed increases.
So will it's speed keep on increasing, or it will get stable?
If yes, ...
1
vote
1answer
55 views
Mean value of the force in a collision problem
I have the following problem:
A point with mass $m$ and speed $v$ collides with a fixed obstacle and penetrates it, stopping in a space $\Delta x$. Calculate $\Delta t $.
I understand the way my ...
2
votes
2answers
217 views
Small car colliding with large truck
A small car collides with a large truck. Why do both vehicles experience the same magnitude of force? Wouldn't the large vehicle experience less force than the small one?
1
vote
1answer
66 views
particle accelerator in space
I'm attempting to learn special relativity and i'm having trouble calculating velocity and momentum for each part of the system after interactions.
I wanted to know how fast a linear accelerator and ...
3
votes
2answers
305 views
block slides on smooth triangular wedge kept on smooth floor.Find velocity of wedge when block reaches bottom
Find the velocity of the triangular block when the small block reaches the bottom:
Here is what I did:
The final velocity(at the bottom)of the small block of mass m is $\sqrt{2gh}$ along the plane ...
4
votes
1answer
154 views
What is the result of a classical collision between THREE point particles at the same precise instant?
Classical Mechanics is said to be deterministic, a statement that nearly always is followed by that quote from Laplace, something like
If at one time, one knew the positions and velocities of all ...
0
votes
2answers
191 views
Can conservation of momentum related to Newton's first law?
I know this is a scrap of thought, but the first law states that (from Wikipedia):
If an object experiences no net force, then its velocity is constant
Is it describing the conservation of ...
0
votes
2answers
104 views
Is air drag equation in term of momentum still valid?
This is the known equation of air drag:
$$m{\bf a}=mg-\mathcal D=mg-b{\bf v}.$$
Considering this, is air drag equation in term of momentum still valid?
$$m{\bf v}=mv_g-b{\bf r}.$$
-1
votes
3answers
168 views
Classical mechanics and the speed of a train-mosquito collision, when perfectly rigid bodies
This is all under the assumption that they are perfectly rigid bodies:
A train is moving at 300m/s.
A mosquito is moving directly towards it, head-on, at 4m/s.
When the mosquito and the train ...
2
votes
1answer
401 views
Elastic collision in two dimensions
Suppose a particle with mass $m_1$ and speed $v_{1i}$ undergoes an elastic collision with stationary particle of mass $m_2$. After the collision, particle of mass $m_1$ moves with speed $v_{1f}$ in a ...
2
votes
0answers
135 views
Early stages of a computational model for object movement charting
We would like to build a computational model capable of accurately predicting the position of any object inside a chamber at any given time.
Inside the model we would have a number of smaller ...
1
vote
3answers
130 views
Displacement with zero velocity
I know that we can rotate a deformable object using internal forces only in space. Thus we can cause an angular displacement without the use of any external forces.
The following youtube video shows ...
0
votes
0answers
26 views
Elastic Collision Between Two Objects [duplicate]
Possible Duplicate:
Elastic Collision And Momentum
I've already asked this question, Elastic Collision And Momentum, but I didn't find the answer particularly helpful--sorry, I don't mean ...
0
votes
1answer
318 views
Elastic Collision And Momentum
The question I am working on is, "Two blocks are free to slide along the friction-less wooden track shown below. The block of mass $m_1 = 4.98~kg$ is released from the position shown, at height $h = ...
0
votes
1answer
114 views
Analysis of the impulse of 2 colliding carts under the effect of magnetic repulsion
Hi there! I have a question about an experiment that was conducted. It is related to momentum.
2 carts were put on a track on opposite sides. They were then propelled towards one another at ...
1
vote
1answer
150 views
Momentum And A Car Collision
I am studying an example problem, concerning the very topic mentioned in the title. In this example problem, a car has a head-on collision with the wall; the initial and final velocity are known, as ...
0
votes
1answer
64 views
A Decrease In Momentum?
The specifics of a question I am working on are, "After a 0.280-kg rubber ball is dropped from a height of 1.80 m, it bounces off a concrete floor and rebounds to a height of 1.45 m."
Why doesn't the ...
0
votes
1answer
122 views
Momentum And Energy Problem
The information to the question is, "A $59.0~kg$ boy and his $38.0~kg$ sister, both wearing roller blades, face each other at rest. The girl pushes the boy hard, sending him backward with a velocity ...
0
votes
1answer
329 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
vote
1answer
96 views
Conservation of momentum with MOND
Assuming as true the phenomenological MOND law for low accelerations ($< 10^{-10} m s^{-2} = a_0$), and considering a small mass $m$ attached to a larger mass $M$ by a faint spring (let's think of ...
1
vote
2answers
150 views
Conservation of Linear Momentum with respect to a given direction
Is linear momentum conserved in any direction? More specifically, if you project all momentum vectors in a system onto another vector, will momentum be conserved?
I know that momentum is conserved ...
1
vote
2answers
959 views
Inelastic collision and conservation of linear and angular momentum
Is it possible for two spheres (a & b) to have an inelastic collision with BOTH the total linear and angular momentum preserved? I'm doing some physics simulation of some spheres attracting each ...
1
vote
3answers
261 views
Same momentum, different mass
The question is: if
A bowling ball and ping pong ball
are moving at same momentum
and you exert same force to stop each one
which will take a longer time? or some?
which will have a longer ...
0
votes
2answers
210 views
Center of mass of a car
This might be little of the track but my question is more on possibility of application of principle of center of mass.
The probability of a vehicle overturning depends more on the level of center of ...
3
votes
1answer
368 views
Simple 2D Vehicle collision physics
I'm trying to create a simplified GTA 2 clone to learn. I'm onto vehicle collisions physics. The basic idea I would say is, To apply force F determined by vehicle A's position and velocity onto point ...
3
votes
3answers
392 views
Newton's 3rd Law: How can I break things?
If I punch a wooden board hard enough and it breaks in two, has the board still exerted a force of equal magnitude on my fist?
When the board breaks in two due to my force, the halves have a ...
3
votes
3answers
248 views
Conservation of Energy in Different Frames of Reference
Say I have a bucket of fuel that can produce 150J of energy by combustion. No matter what frame of reference an observer or the bucket of fuel is in, since the configuration of molecules stay the ...
2
votes
2answers
896 views
Do the physics in the FlyBoard video make sense?
If you haven't seen the video of the FlyBoard, please have a look: http://www.youtube.com/watch?v=Cd6C1vIyQ3w&feature=youtube_gdata_player
Yes, it's amazing, but do the physics make sense or is ...
2
votes
3answers
202 views
Explanation for classic mechanics puzzle
I'm trying to figure out a nice way to describe to a kid the physics behind these experiments:
Assuming ideal conditions, we have a small boat with a sale, close to a lake's shore and a fan fixed on ...
9
votes
1answer
209 views
Can a fly pierce itself onto a cactus needle?
Somebody on reddit posted a ridiculous picture today of a fly pierced onto a needle of a cactus: http://www.reddit.com/r/pics/comments/xarue/what_are_the_odds_of_this_accident/
Whilst the OP claims ...
1
vote
2answers
53 views
Can you launch an item farther by slamming into it or accelerating it along a length
I am trying to desgin a little penny balista toy (built with a 3d printer).
The short description is that there is a track with a mass ("hammer") that slides along it. There is a stack of pennies in ...
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
...
4
votes
3answers
492 views
Why do we need the quantity momentum?
Why do we need the quantity Momentum in physics when we have the quantities like Force and Energy? Isn't it possible to substitute the usage of Momentum with equivalent of Force and Energy?
