Deceleration Definition and 16 Discussions

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,




{\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

    Finding the 'g-force' of a decelerating falling mass.

    Hey all, I need a reality check and verification on some work I have been doing. I feel as though I might be too close to the problem now and am missing something about this. It's also been a few years since I studied physics at University, so I'm a little rusty. Problem: An initially...
  2. ChrisXenon

    Problems with UK A level Physics Marking Schemes

    Hi Folks, I am a private tutor and one thing I teach is A level Physics (OCR Physics A). Am I the only person who has been sometimes baffled and deeply disappointed with some of the questions/answers? Let me explain what I mean. I see questions form which it's not possible to decide what kind...
  3. L

    Speed of a decelerating boat

    Homework Statement A boat, moving at the velocity of 9,9m/s turns off its engine and starts decelerating at the rate of a=-kv^2. What is the velocity of the boat after 4,9 seconds if the constant k is k=5,5m Homework Equations The Attempt at a Solution I tried to integrate deceleration to get...
  4. M

    Finding speed when given deceleration and distance?

    Hi! I have this homework problem that has me completely stumped. Any help is greatly appreciated! In coming to a stop, a car leaves skid marks 80m long on the highway. Assuming a deceleration of 7.00m/s2, estimate the speed of the car just before braking. I just can't figure out what formula...
  5. J

    What if the actual force for a Newton was different?

    ince f=ma, and we derive whatever the force it takes to accelerate a specific mass at a specific acceleration as a unit of force. I understand this ratio of actual force will always be the same in the entire universe but is there a reason why for example 1kg accelerated a 1m/s^2=1 N which is...
  6. L

    Fidget Spinner Deceleration

    Hi All, In a fidget spinner. Disregarding what force applied and spinner decelerate (a) at a given time (t), at what distance (s) it travel before full stop?
  7. T

    Deceleration Going Up a Slope

    Homework Statement Calculate the deceleration of a snowboarder going up a 5.0° slope, assuming the coefficient of friction for waxed wood on wet snow ( = 0.1). Homework Equations F = ma W = mg Fs = (Fn) Fk = k (Fn) The Attempt at a Solution Answer key says it's 1.83 m/s2. I fiddled...
  8. R

    I What causes the deceleration of a satellite? Space dust?

    After talking to a coworker, I looked into the wikipedia article on "Gravity of Earth". I found that the Earth's gravity is not uniform, which makes sense (never thought about it). I have always wondered why satellites de-orbit over time. Someone told me that there is enough space dust to slow...
  9. Vikinglord

    I Skydiving question

    I'm wondering how to calculate the force exerted on a skydiver as they decelerate from their terminal velocity of approximately 120 mph to approximately 30 mph in the course of one second, as I have seen and felt while skydiving. Thank you all in advance.
  10. S

    Is Acceleration/Decceleration smooth?

    Firstly I must say if this is in a wrong sub-forum I apologise. This is my first post and I'm new to the website so please bare with me. Also I was unsure of the Prefix so I again apologise if that to, was incorrect. But my Question is that is the acceleration (or deceleration) of an object...
  11. A

    Finding deceleration of a ball?

    Homework Statement How to find deceleration of a ball that is hit, given the ball: mass=0.1kg F=20N is hit by a bat for 0.01s has an acceleration of 200ms^-2 when hit by bat speed=2m per sec travels 0.01m as it is being hit by the bat Was initially at rest. Homework Equations a=(v-u)/t The...
  12. electrodruid

    What factors affect car braking distance?

    I'm a game programmer trying to write code to simulate a variety of cars braking at different speeds and on surfaces with different coefficients of friction. For now, consider that I'm interested in a fairly wide range of cars (people carriers, hatchbacks, saloons, sports cars etc) but that...
  13. M

    Distance traveled with acceleration & deceleration

    Homework Statement A man bungee jumps off a cliff and free falls for 3 seconds. The bungee cord stops the jumper in 5 seconds. How far did the man fall in total? Homework Equations X = V0t + 1/2at2 The Attempt at a Solution Xf = X1 + X2 X1 = V1it1 + 1/2a1t12 X1 = 0 * 3 + 1/2 * -9.8 * 32...
  14. M

    Find for how much time, the car with stop and how many meter

    Homework Statement A car with mass 1000kg moves with velocity 50 km/hour. The system of deceleration in a car is based on the principle of "force match" that is applied on each of four wheels with a force of 210 N and the ray of the wheel is 0.3m. Find for how much time, the car with stop and...
  15. M

    Finding the max speed of an object between two point

    Hello everybody, I am trying to calculate the maximum velocity(x) an object reaches between two point. The object accelerates from point A to a certain velocity(x) and then decelerates to point B. The acceleration and deceleration are known but are different. The distance from point A to point...
  16. C

    Deceleration on a Gradient

    Hi guys, I'm new to this site so forgive me if I'm unfamiliar with any etiquette unique to here. We did a practical exercise the other day in class in which we accelerated a bogey to a certain RPM and then released it to accelerate up a ramp. We were then given a sheet of the measurements I have...