This tag is for the classical concept of forces, i.e. the quantities causing an acceleration of a body. It expands to the strong/electroweak force only insofar as they act comparable to ‘classical’ forces. Use [tag:particle-physics] for decay channels due to forces and [tag:newtonian-mechanics] or ...
2
votes
2answers
152 views
Fictitious forces confusion
I have a hard time understanding the subject of fictitious forces. Let's discuss a few examples:
1) I'm sitting inside a vehicle which is accelerating in a straight line. I feel like someone is ...
0
votes
1answer
61 views
Do all forces act in the same way where gravity is close to zero?
Suppose that I put in the outer space (where gravity from other bodies is negligible) a large, perfectly round sphere totally filled with water. At the bottom (even though "bottom" doesn't make much ...
-4
votes
1answer
6k views
What is the extent of Earth's gravitational pull?
Where the gravitational pull of Earth exist up to?
What distance from Earth it will be zero?
How do the skydivers fly at a same altitude?
Won't they feel gravitational pull?
What is the Earth's ...
2
votes
3answers
135 views
Is restoring force a particular type of force?
I have a question about the restoring force in elastic band or rope which confusing me for a long time.
As I was told in high school physics, for an elastic band (or spring), if Hooke's law holds, we ...
1
vote
0answers
49 views
Where do electrons get the energy to remain in orbit? [duplicate]
As we know electrons continuously revolve around the nuclus without falling in it at a high velocity beating it's force of attraction. My question is where do electrons get energy to revolve around ...
0
votes
2answers
141 views
Lagrange-Euler equations for a bead moving on a ring
A bead with mass $m$ is free to glide on a ring that rotates about an axis with constant angular velocity. Form the Lagrange-Euler equations for the movement of the bead.
Solution: Let us ...
8
votes
9answers
6k views
What's the core difference between the electric and magnetic forces?
I require only a simple answer. One sentence is enough... (It's for high school physics)
1
vote
2answers
2k views
The most efficient Fan Blade Design
What could be the most efficient fan blade design? There are three main factors for a good fan: one is speed at which air is circulated; second,the volume of air it can circulate; and the third is ...
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
4answers
503 views
Relationship between mass, energy, and a force?
I've never truly understood the relationship between mass, energy, and force. I know what each of the three are, I just don't fully understand how they interact with each other.
For example,
How ...
-1
votes
1answer
250 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?
...
2
votes
2answers
230 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?
7
votes
1answer
173 views
How would nucleosynthesis be different if the neutron were stable?
If the strong nuclear force were just 2% stronger, the neutron would be a stable particle instead of having a half life of about 13 minutes. What difference would that have made to Big Bang ...
5
votes
2answers
245 views
MotoGP motorcycles lift front wheel while exiting curve
I've seen multiple times now in MotoGP that motorcycles were leaving a curve, and because of the acceleration the front wheel is slightly leaving the ground. But at the same time they were still ...
2
votes
5answers
373 views
What is force? How does a constant force output a nonconstant power?
For a constant force, P=Fv. I understand the mathematical derivation of this, but this seems to me, intuitively, to be nonsense. I feel that my discomfort with this comes from a fundamental ...
0
votes
1answer
88 views
Component of force field tangent to a curve
I recently had to solve the following problem:
A force $F=10\hat x- 8\hat y$ is applied to an object that is constrained to travel towards increasing values of x along the path defined by $y=x^2$ ...
0
votes
2answers
247 views
How much work is done when pushing against a brick wall?
So this is one of the questions on my physics assessment and I would like to know how to calculate how much work is done when pushing against a brick wall.
My teacher has told me the calculation is: ...
-2
votes
1answer
125 views
Newton first law of motion, braking suddenly in car
While driving down the road, if you hit the brakes suddenly, your body moves forward. Explain the reason for this.
0
votes
1answer
68 views
What is the significance of Planck force?
I have been curious to find what could be the significance of Planck force? It is calculated by the formula $c^4/G$,
where $c$ is the speed of light; $G$ is the gravitational constant. Thus (the speed ...
1
vote
0answers
38 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 ...
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?
$$m{\bf v}=mv_g-b{\bf r}.$$
3
votes
2answers
218 views
The Double Integrator: Matching velocity and position as quickly as possible with only a limited amount of force available
If a body with mass $m$ begins at position $x_0$ with velocity $v_0$ and experiences a force that varies as a function of time $f(t)$ (and we ignore gravity, friction, and everything else that might ...
1
vote
2answers
103 views
Additional mass of block on inclined plane
I would like some help in solving this problem.
Height is 15 cm , base is 88 cm
My attempt:
$$(119.3 + m)(\sin(\theta)) = (88*9.8)$$
$$ 15^2 + 88^2 = 89.269^2 $$
$$ \sin^{-1} = 15/89.269 $$
$$ ...
5
votes
3answers
307 views
Particle coming across a step potential barrier
My quantum mechanics textbook says that when a particle (in the classical case) comes across a potential-step barrier of finite height, if it has sufficient energy to surmount the barrier, it will ...
1
vote
2answers
108 views
Will a rotating object traveling along a linear path continue to rotate forever in space?
Suppose engineers built a cylinder-shaped space ship which rotates to create artificial gravity:
...
0
votes
0answers
40 views
Help with forces [closed]
The 72.0 kg climber in the figure is supported in the "chimney" by the friction forces exerted on his shoes and back. The static coefficients of friction between his shoes and the wall, and between ...
5
votes
4answers
606 views
Alternate layman's metaphors for illustrating curved space-time
The metaphor of a surface (typically a pool table or a trampoline) distorted by a massive object is commonly used as a metaphor for illustrating gravitationally induced space-time curvature. But as ...
1
vote
1answer
149 views
Force exerted on a cone
This is probably a pretty elemental question, but I can't figure out what the concept is called or how to calculate it. Say you have a solid cone shaped piece of ice, you hold it in your hand and ...
0
votes
0answers
62 views
On a Pilates reformer, how much resistance is from springs and how much from weight of user?
Here's picture of a Pilates Reformer machine: image
How much of the force required to move the carriage is based on the resistance of the springs, and how much is based on the weight of the user? ...
1
vote
1answer
57 views
Charged plane in an electric field acceleration
A perpendicular plane to an electric field's lines of force has more electric flux than a plane that is in parallel with the lines of force, right?
Does this mean that a charged plate would ...
-1
votes
2answers
151 views
A simple logical problem regarding pressure and force
Suppose a 2 meter long pipe, with area of cross section is $1 m^2$. The pipe is vertically placed, with the bottom end closed. Inside the pipe, at the closed bottom end, there is $1 m^3$ of air, ...
0
votes
1answer
236 views
Block Hanging From a Rope [closed]
A block of weight 47.0 N is hanging from a rope. The tension from the rope is pulling upward on the block. The block is accelerating downward at a rate of 1.53 m/s2. What is the magnitude of the ...
2
votes
0answers
47 views
Semiflexible discrete polymer chain
Suppose we have a 2D polymer model described by a set of 2D vectors {$\mathbf{t}_i$} ($i=1,2,\dots N$) of length $a$.
The energy of the polymer is given by:
$$
...
1
vote
0answers
55 views
How can I calculate all of the tensions in the cords? [closed]
I have been stuck on this problem for the last half, and to be honest I don't even no where to begin. I'm being asked to calculate all of tensions for the cords. I know I'm supposed to use $\cos$ to ...
2
votes
3answers
148 views
In projectile motion, what does it mean for the motion along the $x$ and $y$ axis to be independent?
In projectile motion, what does it mean for the motion along the $x$ and $y$ axis to be independent?
This question is referring to the concept of projectile motions.
2
votes
5answers
163 views
Forces acting on a point mass in a spinning rigid body
I have learned that all spinning objects will continue spinning even if no force is acting on it, and the tendency to do so is called moment of inertia. But I wonder about the fact that a single point ...
0
votes
0answers
47 views
An ideal toilet roll on a flat surface [closed]
Suppose we have an ideal toilet roll on a flat surface with the outer end of the roll fixed to the surface. After we give the roll an initial velocity such that the roll unwinds, what happens to the ...
1
vote
0answers
86 views
How much force is required to hold an umbrella?
Assuming a small umbrella (e.g. http://www.amazon.com/ShedRain-WindPro-Umbrella-Close-Size/dp/B001DL5WN0). What are the factors that need to be considered? I assume where I hold the umbrella might ...
3
votes
1answer
491 views
Combining Proportions to get Newton's Law of Universal Gravitation
I've read a little on the history of Newton's Law of Gravitation and noticed that the formula can be separated into 3 distinct parts that lead to the end result of $F_g = G \frac{m_1 m_2}{r^2}$; the ...
46
votes
7answers
3k views
Does juggling balls reduce the total weight of the juggler and balls?
A friend offered me a brain teaser to which the solution involves a $195$ pound man juggling two $3$-pound balls to traverse a bridge having a maximum capacity of only $200$ pounds. He explained that ...
1
vote
1answer
151 views
Work done in projectile motion
A projectile is shot at some inclination to the ground. It falls at another point having R distance from the initial point on the ground. Is there any work done?
If initial velocity vector is $(u\cos ...
2
votes
2answers
123 views
Contact force betweeen 2 objects
Suppose that we have 2 objects next to each other.The object at the left is A and the object at right is B.now we have these situations:
1) we push B to the left.
2) we pull A to the left.(in this ...
5
votes
2answers
163 views
Is there an intuitive explanation for the Southward force caused by the Coriolis Effect on rotating spheres?
From the Coriolis Effect article on Wikipedia, the following with regard to the Coriolis Effect on a rotating sphere:
By setting vn = 0, it can be seen immediately that (for positive φ and ω) a ...
-2
votes
2answers
3k views
How exactly does mass affect speed?
I konw that mass affects weight (force), so how does that relate to speed? F=ma. so how does all this affect speed?
1
vote
0answers
36 views
stopping distance [closed]
if it takes a 4 door sedan x amount of feet to go from 65 mph to 45 mph (and i don't know how many feet that is) on a dry straight road,
how many feet would it take for a large Mack truck ...
3
votes
1answer
62 views
Relation between Casimir and hydrophobic effects
Background
Some years ago I was studying "Fundamentos de biología" (Biology fundamentals) and learned how the lipids create a bilayer due to the water repulsion. Some time later I learned that this ...
0
votes
2answers
724 views
Preventing a block from sliding on a frictionless inclined plane
I want to demonstrate what force $F$ you would have to exert on an inclined plane of angle $t$, mass $M$ to prevent a block on top of it with mass $m$ from sliding up or down the ramp. I worked out ...
3
votes
1answer
161 views
Is there any case in classical mechanics where Newton's (strong) third law doesn't hold?
Is there any case in classical (non relativistic) mechanics where the strong form of Newton's third law does not hold (that is, reaction forces are not collinear)? For example, if we consider a system ...
8
votes
2answers
245 views
What IS Color Charge?
This question has been asked twice already, with very detailed answers. After reading those answers, I am left with one more question: what is color charge?
It has nothing to do with colored light, ...
0
votes
0answers
213 views
How to calculate the force between two different magnets?
I'm doing an experiment and I need to calculate the force between two magnets with different stats, different sizes and flux density.
I learned physics in high school so I know all the terms.
In my ...
