# What is Accelerate: Definition + 191 Threads

In mechanics, acceleration is the rate of change of the velocity of an object with respect to time.
Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by the orientation of the net force acting on that object. The magnitude of an object's acceleration, as described by Newton's Second Law, is the combined effect of two causes:

the net balance of all external forces acting onto that object — magnitude is directly proportional to this net resulting force;
that object's mass, depending on the materials out of which it is made — magnitude is inversely proportional to the object's mass.The SI unit for acceleration is metre per second squared (m⋅s−2,

m

s

2

{\displaystyle {\tfrac {\operatorname {m} }{\operatorname {s} ^{2}}}}
).
For example, when a vehicle starts from a standstill (zero velocity, in an inertial frame of reference) and travels in a straight line at increasing speeds, it is accelerating in the direction of travel. If the vehicle turns, an acceleration occurs toward the new direction and changes its motion vector. The acceleration of the vehicle in its current direction of motion is called a linear (or tangential during circular motions) acceleration, the reaction to which the passengers on board experience as a force pushing them back into their seats. When changing direction, the effecting acceleration is called radial (or orthogonal during circular motions) acceleration, the reaction to which the passengers experience as a centrifugal force. If the speed of the vehicle decreases, this is an acceleration in the opposite direction and mathematically a negative, sometimes called deceleration, and passengers experience the reaction to deceleration as an inertial force pushing them forward. Such negative accelerations are often achieved by retrorocket burning in spacecraft. Both acceleration and deceleration are treated the same, they are both changes in velocity. Each of these accelerations (tangential, radial, deceleration) is felt by passengers until their relative (differential) velocity are neutralized in reference to the vehicle.

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1. M

### Electric motor problem -- Power to accelerate a toy train

For part (b), The solution is, However, if the acceleration was not constant during the 21 ms, then would the power required be larger? I believe the average power required would be larger because if the train started off at a lower speed and then speed up very rapidly towards the end...
2. ### Net work and kinetic energy (pushing a wagon to accelerate it)

I'm a little confused because my teacher used Bill's 500J of work for the kinetic energy equation and I don't understand why. I used the net work, so 300J, to find the speed and I'm not sure why that's wrong. Wouldn't friction make the wagon move slower than if there was no friction? So why...
3. ### B How come friction can make a car turn?

How is it possible that friction makes car turn? From what I know, frictional force is acting along to the direction of the wheel turns. When the car turns, the direction of the frictional force now act opposite to the direction of the wheel turns! I'm sure if you rotate the steering wheel to...
4. ### MHB Accelerate Zero-Knowledge Cryptography with ZPrize!

I would like to invite your members to participate in the ZPrize competition. ZPrize is an industry-wide competition, modeled after the XPrize, to accelerate zero-knowledge cryptography. We have over 39 leading zero-knowledge technology companies contributing to this effort donating \$7 million...
5. ### B Can Accelerate at Constant g in Own FoR?

( This question came up in the context of flat earth. Sorry for that, but hopefully the question itself is not dumbtarded. ) Basically one "model" for gravity that some FErs subscribe to, is that the Earth disc is accelerating upwards at 9.8 ms-2. And one debunk of this proposition was that the...
6. ### Science enthusiast wanting to accelerate my learning

[Mentor Note -- Thread moved from the New Member Introductions forum] How did you find PF?: google search I am a middle school student and have a deep passion for physics, I want to understand quantum mechanics and relativity. Physics according to me is the most precise description of nature...
7. ### Find the power needed to accelerate this elevator downward

An elevator of mass M is accelerating downward with constant acceleration A. Friction force acting on the elevator is constant and given by f (The initial speed of the elevator is zero.). Find the power generated by the engine of the elevator (in terms of M, A, g, f, and time t). For this...
8. ### Force to accelerate an object downward faster than g

Hello all. I am trying to understand the math behind this and keep getting stuck. If I want to accelerate and object downward,lets say 16 inches in 0.1655 seconds , that would be faster acceleration than gravity. I think 29.67 m/s2, so if I calculate force to accelerate at that rate downward...
9. ### I Do you accelerate through time when you stand still on Earth?

Disclaimer: I'm not actually sure which acceleration is proper and which is coordinate, and I can't recall the source for the half-remembered equation. I spent some time going through my bookmarks, but it was to no avail. Sorry about that. So, general relativity removes the idea of gravity as...
10. ### Does it take longer to accelerate from high speed to higher

I wanted to ask this question for very long . lets say we have rocket in mass of 1kg in space that moving in speed of 100 m/s if we want the rocket to speed up, we need to spent some energy that equal to mv^2/2. in our case it 1*200^2/2 it 2000 Minos the energy we already have which is...
11. ### Force required to accelerate upward against gravity

So I am working on a project where I am attempting to accelerate an object upward Against Gravity but I am having trouble figuring out the math behind the force needed to do this here is what I have come up with so far,my apologies I am not very good with math I found this equation W=m(a+g)y...
12. ### Why does the big block accelerate?

Clearly, in the picture I can see that on the small block on top, tension and gravitational force act. Gravity gets balance by the normal force, so tension is the only force causing acceleration. On the block at the side gravity and tension result in vertical acceleration. However, I do not...
13. ### Mechanics: Two masses on a pulley causing two cylinders to accelerate

Hi! I need help with this problem. m1-2-3-4 and R are given. There is no slip in the system. I have to give F1-2-3-4 in respect of the masses and R. Here is what I managed to m1 is easy: m1*a = m1*g - T(tension of the rope) m2: m2*a = T - (?) <-- I have a problem with this. F1 and F3 is the...
14. ### Power To Accelerate 1000kg Elevator Cab Upward

(a) When the cab is carrying its maximum capacity, at what rate must the motor deliver energy to get the cab up to cruising speed? My shot was finding the acceleration, a=1.5/2 = 0.75m/s2 Displacement of elevator Vf2 = vi2 + 2aΔx Δx = 1.5m Force of elevator (Since it accelerates...
15. ### I Why don't Cooper electrons accelerate infinitely?

Hello, I am trying to learn Quantum mechanics and have some questions I cannot answer. cooper pairs, composite boson particles (spin number = 0 or 1) from two coupled electrons. The movement of cooper pairs is forming a superconducting current. Superconducting current does not have a...
16. ### Can Space-Time Differ for Ionized Fuel in a Magnetic Field Near Light Speed?

Summary: Can a particle accelerator accelerate gaseous fuel? Does space-time differ for detonating ionized fuel moving near the speed of light within a magnetic field such as a particle accelerator?
17. ### B Do electrons accelerate when transitioning from one energy state to another?

Do electrons have motion or they just accelerate when they get enough energy?
18. ### Torque required at the wheels to accelerate a vehicle at a certain rate?

I'm struggling to understand something basic here. If I have a just a wheel, with mass 10kg, and radius 0.25m, and I specify that the CG is accelerating linearly at 1ms-2, how do I calculate the force needed to do this? Using F = ma gives 10N, but using this value for torque calculation on the...
19. ### Need a force to accelerate an object on a frictionless surface

Problem Statement: would you need a force to accelerate an object on a friction-less surface? How could one calculate the force? Relevant Equations: F=MA would you need a force to accelerate an object on a friction-less surface? How could one calculate the force?
20. ### Time needed for a Force F to accelerate the crate to 2m/s? (Dynamics)

So above is the question. The picture below is my attempt at the solution: However the answer at the back of the book suggest that T=1.929s
21. ### Does dropping a Jupiter from the Pisa tower still accelerate at g = 9.81?

im confused about this thing, because they said Earth's acceleration due to gravity is independent from the mass of the thing dropped
22. ### B Why do things in free fall accelerate?

Hello, I have a problem to understand acceleration in GR, objects in free fall move along a geodesic, they are in inertial motion. But observer on Earth can clearly see that falling thing accelerates. What causes the acceleration, when there is no gravititional force? Thanks for answers.
23. ### I How much does the Universe accelerate?

Please clarify. I have read that according to NASA the universe's expansion rate is 74.3 km/s +/- 2.1 at Mega parsec. At a distance of one Mega parsec, space is moving 74 km/s away from us. At 2 Mega parsec it is moving away at 148 km/s. Do I understand this correctly? But this is velocity, it...
24. ### Kinematics within a simulation

Homework Statement I'm simulating a warehouse (in Unity) where forklifts and other vehicles transport stuff from point A to point B. The routes are modeled as a graph with vertices and edges. Every transport is saved as a task in a backend system with the relevant data such as starting time...
25. ### B Gravity Power: What Gives It the Ability to Accelerate Objects?

What is the physical property that gravity has that enables it to make an object go faster or, if it is resting on the ground, have weight? In General Relativity (as I understand it) objects in free fall move in geodesics. Thus an orbiting satellite moves in the curve around the planet that is...
26. ### What gives gravity its power to accelerate objects?

What is the physical property that gravity has that enables it to make an object go faster or, if it is resting on the ground, have weight? That means it can do work: it gives objects kinetic energy. Where does that ability come from and where does the energy (the gravitational potential...
27. ### Air drag force: Why heavy objects accelerate faster?

I've done the math but because i can't find this answer anywhere in the book which I'm reading and on the web, I would like to be sure if my calculations are correct. I know that if two objects (starting at the same time) are free falling without a drag force being applied to them, the...
28. ### Limits to accelerate a spacecraft by spinning it in a circle

The basic concept is to have your space probe(s) - likely nanocraft [1] on a spinning object in space which allows you to preserve the momentum you give it while accelerating it faster. Then once you are at a speed you can simply release the nanocraft in the direction you want it to go in. More...
29. ### Finding the torque needed to accelerate a wheel

Homework Statement Object of fifty kg and a r= 0.025m. What's the torque to accelerate from 0 to 0.4 in 20s. Homework Equations Torque = Moment of inertia * angular acceleration T = I * α The Attempt at a Solution [/B] m = 50kg r = 0.25m α = (0.4) / 20 = 0.02 I = mr^2 = 50 * 0.25^2 =...
30. ### I Can a Gravitational 'Gun' Accelerate Objects?

Hello, Special arrangements of charged material can be used to accelerate charged objects or particles, e.g. a cathode ray tube. I am just wondering if it would be somehow possible, in principle if not in practice, to accelerate objects with gravitational force using special arrangements of...
31. ### Energy required to accelerate itself

Hi. The energy required to accelerate an object of mass ##m## to a speed ##v## is ##E_k=\frac{m}{2} v^2##. But how much energy does an object need to accelerate itself to ##v##? Say, how much fuel (in energy units) does a car need to accelerate to ##v##, if there are no air resistance or...
32. ### Why Doesn't My Power Calculation Match Real-World Scenarios?

Homework Statement Hi, guys. I'm in a bit of a quandary. I'm trying to calculate the power a motor should have in order to move a mass a certain distance. My calculation keeps telling me that the horsepower output is much lower than my reference scenario. Here's the situation. I'm trying to...
33. A

### Quick Question on Van de Graaff Particle Accelerators

Hi everyone. Just a small, quick question I have: Can negative ions be accelerated by a Van de Graaff particle accelerator? My initial reaction is no, because the terminal (the sphere with the charges allocated on the outside) is positive, which means negative ions would be attracted and not...
34. Y

### Why does it take more energy to accelerate faster objects?

Let's say we have a 1kg object and the reference point is the ground. Accelerating it from 0 to 1 m/s takes 0.5*1*1^2 - 0 joules, which is 0.5 joules. But accelerating it from 10 to 11 m/s takes 0.5*1*11^2 - 0.5*1*10^2 joules, which is 10.5 joules. This doesn't make much sense to me as the...
35. ### Can Light Accelerate When Changing Direction?

I know that light is always at constant speed but does it ever accelerate when changing direction, if you put light through lots of different densities it curves into the Brachistochrone curve, would that be an instance of light acceleration.
36. ### B Does an object moving in a geodesic accelerate?

So in GR, objects orbiting the sun, for example, move in a geodesic - a straight line something curved. Without GR (using Newtonian Gravity), I can easily say because planets orbiting the sun are doing so in a ellipse, they are accelerating. However, would they still be accelerating when you add...
37. ### Average Acceleration and Time Taken to accelerate

Hi, I've been asked to solve below as part of an assignment. Below is pretty much what I've submitted but it has been concluded to be incorrect. I am unsure as to why hence the question. Is it due to the fact that I have not taken the mass or forces into consideration? I have only taken these...
38. ### Determine torque required to accelerate the flywheel

Homework Statement A solid disk of diameter equal to 500 mm and a mass of 60 kg is to be used as a flywheel in an energy recovery device. Determine the torque required to accelerate the rotation of the flywheel, about its axis, from rest to 250 rpm in 6 revolutions. Homework Equations [/B]...
39. ### How much energy is required to accelerate a charge?

Lets suppose we have a charge and we want to accelerate it from a point A to B and back. Does the energy requirement increases if we move the charge quicker? I can make an analogy with mass. To accelerate an object over a distance d requires energy. The objects resist to change in velocity. The...
40. ### Energy to accelerate an 1kg object to 0.9965c?

Homework Statement How much energy does it take to accelerate an object of mass 20,000 kg from rest to 0.9965c? m = 20,000 kg v0 = 0 m/s vf = 0.9965c Homework Equations ## E^{2} = \sqrt{(pc)^{2}+(mc^{2})^2} \\ E_{KE} = (\gamma - 1)mc^{2} \\ \gamma = \sqrt{\frac{1}{1-(v/c)^{2}}} \\ p = \gamma...
41. ### Torque needed to accelerate rail-mounted vehicle

<Moved from a technical forum. Therefore no template.>I am currently analysing the forces acting on a moving vehicle. The vehicle is mounted on a rail with wheels on both upper and lower side of the rail with a spring increasing the reaction force, and thereby the friction. The vehicle should be...
42. ### Do charges accelerate because their field lines are changed?

I ask this because of this diagram. Say that two charges are held a certain distance apart and are let go. Well, we see that the field lines of one charge repels the other. And I noticed that the field lines for an accelerating charge also bends. So can we say that because one field...
43. ### I How did scientists figure out the expansion is accelerating?

I understand that the acceleration of the universe's expansion was discovered by looking at very far away Type 1a supernovae. My question is how was the data used exactly to calculate the Hubble constant in the past and then compare it with today's value? Did they simple plot the distances...
44. ### How can the end of a rod accelerate faster than g?

A uniform rod rests on supports at its ends. The right support is quickly removed. The atom on the right end will accelerate faster than ##g## at ##1.5g##. How is this possible forces-wise? The only forces acting on the atom is its own weight and the interatomic forces of attraction, which...
45. ### Find the net work required to accelerate a cylinder

Homework Statement A merry-go-round has a mass of 1440kg and a radius of 7.50m . How much net work is required to accelerate it from rest to a rotation rate of 1.00 revolution per 7.00s? Assume it is a solid cylinder. Homework Equations I believe my relevant equations are: ICYL=½mr2 ω=(Δθ/Δt)...
46. ### Why do objects accelerate with a net force?

Why do things accelerate? Let's take a falling object for example, why does it accelerate towards the Earth? I know that when a net force acts on an object, it accelerates but THAT is my question, why does this happen? Why wouldn't the velocity stay the same with a net force acting on an object...
47. ### Can a Tiger Outrun a Lion in a 100 Meter Dash?

Homework Statement In a 100 m race between a lion and a tiger, the lion starts from rest and accelerates at a rate of 2 m/s2 for 5 seconds, then maintains a constant velocity for the rest of the race. The tiger starts from rest and accelerates at a rate 3 m/s2 for 4 seconds, then maintains a...
48. ### I Can an object accelerate at a constant pace forever?

Considering special relativity, let us take an object accelerating at a rate of 6m/s^2. Let's say that this object is large enough for an observer to securely stand on it while it is accelerating. Would this object be able to accelerate at this rate forever without reaching the speed of light...
49. ### Can a 400V 2200µF capacitor propel 0.5g through a rail gun?

I am planning to conduct an academic experiment involving an electromagnetic projectile. I originally planned to build a rail gun powered by a 400V 2200µF capacitor, I've read a lot of discussions that say rail guns require a tremendous amount of current. Is this capacitor sufficient to propel...
50. ### Using orbital spin to accelerate an interstellar launch

Ok, so I know I'm missing something here. But, you know how pool balls that rotate opposite direction increase the speed of one of them through kinetic transfer? Why don't we build a launch platform based on this approach and use the orbital spin of the Sun, Jupiter, and Saturn (gaining speed...