In Newtonian physics, free fall is any motion of a body where gravity is the only force acting upon it. In the context of general relativity, where gravitation is reduced to a space-time curvature, a body in free fall has no force acting on it.
An object in the technical sense of the term "free fall" may not necessarily be falling down in the usual sense of the term. An object moving upwards might not normally be considered to be falling, but if it is subject to only the force of gravity, it is said to be in free fall. The Moon is thus in free fall around the Earth, though its orbital speed keeps it in very far orbit from the Earth's surface.
In a roughly uniform gravitational field, in the absence of any other forces, gravitation acts on each part of the body roughly equally. When there is no normal force exerted between a body (e.g. an astronaut in orbit) and its surrounding objects, it will result in the sensation of weightlessness, a condition that also occurs when the gravitational field is weak (such as when far away from any source of gravity).
The term "free fall" is often used more loosely than in the strict sense defined above. Thus, falling through an atmosphere without a deployed parachute, or lifting device, is also often referred to as free fall. The aerodynamic drag forces in such situations prevent them from producing full weightlessness, and thus a skydiver's "free fall" after reaching terminal velocity produces the sensation of the body's weight being supported on a cushion of air.
To write ##v## as a function of time, I wrote the equation ##m\frac{dv}{dt} = c_{2}v^2 + c_{1}v - mg \implies \frac{mdv}{c_{2}v^2 + c_{1}v - mg} = dt##
To solve this, I thought about partial fractions, but several factors of ##-c_{1} \pm \sqrt {c_{1}^2 +4c_{2}*mg}## would appear and they don't...
Homework Statement
A drop of water fall towards the ground with initial mass [m][/0] and radius [r][/0] (assume the initial shape of that water drop is sphere). the air resistance is F=½.ρ.A.[v][/2].C (C is the drag coefficent, A is the area that the air contact with the water drop and ρ is the...
The set-up of the system is like the following:
The thing is, a weight was attached to the meter stick and it was placed in different locations. Then the system composed of the meter-stick and the added weight was then released and the time it took for the meter stick to hit the floor was...
Here we consider a black hole formed by gravitational collapse classically. We also consider a scalar massless Klein-Gordon field propagating on this background.
To quantize the field we expand it in appropriate modes. The three sets of modes required are:
The incoming modes, appropriate for...
The Setup is the cart-pulley-hanging mass or Atwood machine: if the cart is allowed to fall over the edge, and falls freely with the mass, will the rope tension remain the same as it was before the cart went over the edge? Is this situation the same as if the cart-rope-mass were held aloft by...
Homework Statement
A flower pot is knocked off a window ledge from a height
d = 21.6 m
above the sidewalk as shown in the figure below. It falls toward an unsuspecting man of height
h = 1.71 m
who is standing below. Assume the man below requires 0.300 s to respond to a warning. How close to...
Consider an electric dipole consisting of charges ##q## and ##-q##, both of mass ##m##, separated by a distance ##d##.
If the dipole is given an acceleration ##a## perpendicular to its moment the total electric force on it, due to each charge acting on the other, is given approximately by...
So I'm going to try to keep this as brief as possible, but I have a somewhat advanced physics question that my nuclear background hasn't prepared me for and I need an argument settled at work.
Say you have a 30 ft deep pool and you need to protect the contents, which comprise the bottom ~10 ft...
Homework Statement
A closed funnel is 10 meters above a weighing scale. At t=0 we open the funnel. and 15kg of sand are coming out of it every second. The velocity of the sand when it comes out is 13m/s, directed downwards (towards the scale). At a certain moment the scale displays a value of...
Homework Statement
A rope of length L and mass m is attached to the ceiling and folded at mid length. The free end of the rope is held against the ceiling, then dropped at time t=0.
a) Calculate the velocity of the free end as a function of y, its distance from the ceiling.
b) Calculate R...
Homework Statement
This question is actually two question. We have two hollow frames - one is rectangular and another is triangular. the rectangle is rotated and fixated such that the angles in shape are ##\alpha , \beta = 90 - \alpha## and the angle of triangle is ##\alpha##. We have two balls...
Hi All.
I'm new here so I hope you will bear with me and please tell me if this is out of context or in the wrong part of the forum.
I am trying to programm a falling pipe system with corners in ArchiCAD (GDL).
I have been programming in different languages for a while now, but new to 3D vector...
Homework Statement
We drill a hole from the surface of the Earth to the other side through the center, drop a test particle and measure the time it takes to come back. How does this time depend on the radius and density of the Earth?
Homework EquationsThe Attempt at a Solution
The gravitation...
Heey everyone,
I was wondering how long it takes for a small mass to reach the Earth from infinity . The trajectory is completely radial, so it's a relatively simple equation.
$$r''(t ) =\frac{ - GM} {r(t)^2}. $$
But what if we multiplied both sides by ##2r'(t) ##. Then it follows,
$$2r'(t)...
Today I was thinking how would I calculate the amount of force I would experience if I were to jump out of a second floor building in the event of a fire and if I had to jump how much force would be applied to me? I was able to find the height of the building by dropping an object from rest out...
Homework Statement
A 2 kg ball (k factor of 0.02 m-1) is in free fall. The initial downward velocity of the ball is 12 m/s. Find the difference in displacement after 1s both with and without air resistance.
Homework Equations
vf = vi + at
y = yi + 1/2(vi+vf)t
y - yi = vit + (1/2)At2 - (1/3)Bt3...
Homework Statement
A spigot pours beans onto a scale platform.
At a time t = 0.0 sec, the spigot is opened and beans begins to pour out (with initial velocity 0) at a rate of 1.00 kg/sec onto the platform from a height of 10.0 m above.
(a) At t = 10.0 sec, what is the weight of beans on the...
Homework Statement
I uploaded the homework question. This is #1.
Homework Equations
None directly given
The Attempt at a Solution
My main difficulty with the problem is that I am convinced it is much easier than my classmates make it out to be. This is graduate mechanics so I'm pretty sure...
Homework Statement
Raindrops fall from a broken gutter at 1.0 s intervals to the ground , 19.6 m below
Neglecting air resistance and taking g as 9.81 calculate
the time for each drop to reach the ground
velocity of the drops as they reach the ground
speed of drop at the height of 14.7 m
I...
Homework Statement
"A falling object travels one-fourth of its total distance in the last second of its fall. From what height was it dropped?"
Reference: Up is (+)
Scenario 1 (Complete motion)
a = -9.8
v1 = 0
d = -x
v2 = ?
Scenario 2 (Motion at the last second)
a = -9.8
d' = (1/4)(-x)
t' =...
A freely falling body (falling in earth) accelerates with time. However, an object inside the body remains at rest (if it was initially at rest) or moves with a constant velocity if it was initially moving with constant velocity. In other words a frame fixed to the body is an inertial frame...
Why is the time it takes for a vertically thrown ball to reach max height the same as the time it takes for the same ball to fall from max height to ground level?
I agree with this logically but I can’t prove it mathematically...
Can you please show me the mathematical proof for this fact...
If I was attempting to calculate the amount of energy transferred as heat to an object free-falling in the atmosphere, is this how I could go about it?...
Work = (Drag Force) x (Displacement through atmosphere) = Energy transferred as Heat
I am attempting to solve a hypothetical question...
Hi, I have the following problem:
Given the 5-D generalization of the Schwarszschild solution with line element:
ds^2=-\Bigg(1-\frac{r^2_+}{r^2}\Bigg)dt^2+\Bigg(1-\frac{r^2_+}{r^2}\Bigg)^{-1}dr^2+r^2[d\chi^2+\sin^2(\chi)(d\theta^2+\sin^2(\theta)d\phi^2)]
where ##r_+## is a positive constant...
Looking to develop something that will "hang" as shown in the drawing without falling off and without requiring permanent attachment. Any help appreciated.
Homework Statement
If a falling object overcome 72 metres in 6 second, how much distance it overcame in first 3 second.
Homework Equations
s = ut+(at^2)/2
The Attempt at a Solution
Here,
s = 72 m
u = 0
t = 6s
a = ?
We know,
s = ut+(at^2)/2
Or, 72 = 0*6 + (a*6^2)/2
Or, 72 = 36a/2
Or, 72 = 18a...
A few years back when I was quite young I stumbled upon this.I'm asking whether this is plausible. I'm guessing it isn't, since the chair hasn't absorbed any of the falling force, and you are still traveling at the same speed of descent, just wanted to discuss.
Hello
We stop the moon on its orbit around the earth.
Oups. The moon falls on the earth.
Or.
We bring Jupiter at 400000 km from the earth.
And Jupiter falls on the earth.
Are the fall times the same?
Have a nice monday
Lucw
Homework Statement
What is the speed of a 5 mm steel ball falling through water at 10 C[/B]
Viscosity of water: 1.3059 * 10-3 Pa*s (Various online sources)
Homework Equations
Laminar flow:
Vt = gd2 (ρp - ρm)/18μ
Vt = terminal velocity
g = gravity (10m/s2)
d = diameter of ball
ρp =...
I explain it better. If we bring an electron from higher to lower energy level, the energy gap will be emitted as electromagnetic wave, because of the conservation of energy. When the same situation applies for a physical body, for example letting if falling down from some height, what does it...
Homework Statement
Homework Equations
f=ma
v^2/r
The Attempt at a Solution
I am confused about this question because i am not given an angle theta for the normal force on the ball.
My x component has only the normal force, my y component has only the gravitational force.
I set my y...
Homework Statement
Homework Equations
m:mass of solid cylinder
T: tension in string
w:angular velocity
The Attempt at a Solution
m(g-a)=T
mg-ma=T
a=v^2/r=w^2r
now what?
Hello everyone,
"Does a charged particle radiate in free-fall?".
I read many threads on this subject and I was surprised to find out that there is no unanimous "Yes or No" answer to this question. Here is an interesting answer from researchgate.net:
The question is widely discussed in the...
Homework Statement
A meter stick is held 60 degrees to the horizontal on a flat frictionless surface. If it is let go what is the distance the back the stick will reach with respect to the length of the meter stick (l).
Homework Equations
I = 1/3 mL^2
Don't know what to use. This seems more...
Imagine that you are using an elevator and - due to some cause - all of the cables supporting it cracked and the brakes were not engaged - the elevator is in a free fall. Now, would it be technically possible to jump in that elevator?
Jumping requires the force of reaction of the ground, this...
Hy folks,
Upfront I want to apologize for my writing and my dissability to use correct symbols to ease readability of the example. Ok now that that's done I just want to start upfront.
If we set a usual example of an object falling from a tower with a height of x meters and assume that the...
Homework Statement
The reason why the heavy stone and light stone fall equally because of the ration of force to mass is same. can you explain it please what is ratio of force to mass is same?.
Homework Equations
F=ma and F=Gm1m2/r²
The Attempt at a Solution
As their acceleration is same...
Hello, I am a new member looking for the answer to a question I recently had on an exam. I will not know if I got it right for up to 6 weeks so am curious.
Question is: A faucet drips water at 5 drops per second. calculate the distance in metres between the first and second drop after the first...
I've read other posts about this but I don't think this question was covered.
Say you have two objects with different masses in a vacuum sitting on some kind of plank. Next, you remove the plank from both at the same time. The heavier object has a greater inertia, which means that it has a...
Homework Statement
A collection of neutrons, nominally at rest, are confined in a region 1.0 nm wide on the x-axis at a height of 50 cm above a neutron detector. The neutrons are released and fall under the influence of gravity towards the detector which records the horizontal position of the...
Homework Statement
a uniform fine chain of length l is suspended with lower end just touching a horizontal table. Find the pressure on the table, when a length x has reached the table..
Homework Equations
Pressure = force/area
The Attempt at a Solution
let mass density, m= mass/l...
Homework Statement
A boy release ball A from height 5m from ground at the same time other boy throw ball B vertically upward to exactly strike ball A. When ball B released it was 1m from ground find minimum initial velocity of ball b. Given g=10m/s^2
a) 2m/s b) 3m/s c) 4m/s d) 5m/s
Homework...
Homework Statement
Homework EquationsThe Attempt at a Solution
The option (a) says that the 1st coin remains at its earlier position. Due to gravitational force, the 1st coin falls down, hence option (a) is wrong.
I don’t understand the difference between option (B) and (C).
In my opinion...
Homework Statement
Here is a link to the problem: https://imgur.com/a/0T9sF
I am having trouble finding the time it takes the loop to leave the field in part a.
Homework Equations
## emf=-\frac{d \Phi}{dt} ##
## \Sigma F=ma=mg-BIl ##
## \frac{dv}{dt}-\gamma v=g ## where ##...
Homework Statement
A small but very powerful bar magnet falls from rest under gravity through the center of a horizontal ring of conducting wire, as shown in the figure below (on the left). The speed-versus-time graph, in arbitrary units, of the magnet will correspond most closely to which of...
If an object with 1kg mass falls free (no air drag), from 100 meters high, and the gravitational acceleration is 9.81, then the mechanical energy will be: 1*9.81*100 = 981 joules.
The work the gravitational force does on the object will be: 9.81N*100m = 981 joules.
Another object with same...
Homework Statement
The two blocks, m1 = 3.3 kg and m2 = 4.8, in the figure below are connected by a massless rope that passes over a pulley. The pulley is 12 cm in diameter and has a mass of 2.0 kg. As the pulley turns, friction at the axle exerts a torque of magnitude 0.64 N · m. If the blocks...
Homework Statement
Estimate the time between each photoflash of the apple in Fig. 2-18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
Homework Equations
All we have learned in class is...