What is Braking: Definition and 197 Discussions

A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction.

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  1. Strato Incendus

    How Can a Ship Safely Brake in Space Without Crushing Its Inhabitants?

    The two most unscientific words in Star Trek are probably "full stop". :wink: The Impulse Drive is described in the Voyager Technical Manual as 0.25 c (25% of the speed of light). Whatever g forces are required to "immediately" come to a halt from that speed - it's certainly way beyond what the...
  2. sanderalan

    Energy recovered from a regenerative braking system

    Start velocity is 100 km/h, at 1.5g for 0.5 seconds the end velocity will be 73,52 km/h. So the energy can be calculated if the mass is present, but it is not given. Is there a way to calculate the regenerated energy with the given information?
  3. A

    I Ship Braking: Blue or Red Doppler Shift?

    Let's imagine we have a ship heading towards our planet. It fires forward thrusters to brake. The ship is long way away. Because the ship decelerates, (slows down towards us) would we see particles from its exhaust doppler shifted blue or red? On the one hand the gas is flying towards Earth, so...
  4. P

    Qualitative explanation of Magnetic Braking

    When a magnet moves near a non-magnetic conductor such as copper and aluminium, it experiences a dissipative force called magnetic braking force. I am rather confused by the following explanation of magnetic braking force: The non-magnetic conductor here is the aluminium 'wall' seen on the...
  5. A

    Determining the maximum braking power using derivations

    Hello! So what I've tried to tackle this problem is derive the equation,set it equal to zero,find a value for v and than put it in the second derivation.So when I derive this I get $$ \frac{v^2+9-v *(2v)}{v^4+8v^2+16)} $$ Now if i set that equal 0 and try to find a value for v I get this. ##...
  6. C

    Is the Braking Force of a Truck Really 0.8?

    Hi guys I'm a truck driver. Not sure if I'm posting in the right place so i apologise. Iv'e been on a course today about trucks. The course leader was talking about forces. A trucks force forwards can be 0.8. Is this true?
  7. jaumzaum

    Question about car braking and tire friction

    I'm a little confused about this question because I think the braking deceleration probably takes into account the braking system of the vehicle as well as the power of the motor. I don't understand how a car could actually brake without the "friction between the mechanical components of the...
  8. rbh

    Linear motion, motorcyclist braking time

    I tried using equations listed above to get the answer, but I get stuck with a and Vi. What am I doing wrong? The answer is 6.7 seconds.
  9. iVenky

    Automotive Engine mechanisms during coasting (in drive mode) and engine braking

    I am trying to understand what happens in the engine (especially gasoline vehicles) during coasting (in drive mode) and engine braking. It looks like both mechanisms shut off the fuel injectors. Then how is the former (coasting in drive mode) able to use the momentum while the latter (engine...
  10. D

    How to calculate magnetic braking force?

    I want to know how to calculate the braking force acting on a magnet falling through a copper tube. The setup can be seen in this video (YouTube, @ 1:49 - 3:12): Copper's Surprising Reaction to Strong Magnets. Note that it's not a copper tube in the video but a plastic tube surrounded by a...
  11. R

    I Downhill Bicycle Braking Question

    I ride gravel bikes on steep mountain roads and on the way down I have to ride the brakes pretty hard. I want to minimize brake heat so I have always thought that keeping the bike's velocity lower on average by applying the brakes more often will reduce the amount of energy the brakes will have...
  12. N

    How does regenerative braking vary the load?

    Lately, I've been reading about the electronics required for driving motors and naturally that transitioned into braking. I think I have a decent grasp on resistive braking but I do not fully grasp regenerative braking. This plus googling gaps in my knowledge have been my primary sources...
  13. J

    I The effect of Faraday braking on the Earth’s orbit

    If you let a magnet free-fall down a copper or aluminum tube, the induced magnetic field in the surrounding conductive medium imposes a braking effect on the magnet, reducing its speed (explained by Lenz’s law). The earth, being a large magnet, is essentially free-falling around the sun. The...
  14. A

    The Physics of Truck Braking: Why Shorter Distances When Sliding?

    The truck stops in a shorter distance if the crate slides but why is this the case considering that friction on the crate does positive work on the truck, since it points left for the crate but right for the truck thereby opposing the braking force? I understand why using the equation 1/2mv^2 =...
  15. hugo_faurand

    [Mechanics] Calculate the braking torque

    Hello everyone ! I've got a problem in engineering class with a braking system (picture linked). In the first part I calculated the friction force $$ \vec{B} $$ with components : T (following y axis) : 2073.6N N (following x axis) : 5760N. For the first question I struggle a lot because I...
  16. M

    Engineering Design a go kart braking system

    i have been stuck on this question from my assignment, i have tried solving it in many ways, but apparently i am either bad at this or i just don't understand the question haha. * As a prudent engineer, the main shaft is now subjected to loading condition when only brake is applied. Show with...
  17. ELTSR02

    Magnetic Braking: Pendulum Strength Req. for Effects

    How strong does a permanent magnet/electromagnet need to be in order to see the effects of magnetic braking on a flat metal pendulum?
  18. brotherbobby

    How Does Braking Compare to Turning in Avoiding Collisions?

    1. For the car to apply brakes, we have ##v^2=2ar⇒a=\frac{v^2}{2r}=μg\;\;[ma=μmg]⇒v=\sqrt{2μgr} ## 2. For the car to go in a circle ##\frac{mv^2}{r}=μmg\Rightarrow v=\sqrt{\mu gr}##. We find from above that the maximum velocity ##v## possible to avoid a collision is ##\sqrt{2}## times as much...
  19. trurle

    Braking spacecraft in a snow-filled tank?

    Reading recently a Russian MOD aerospace journal, i stumbled upon (pretty unrealistic) scheme to hard-land payloads (metal ingots) on moon. It involve catching 1.7 km/s slugs with the pipe filled by regolith or water, and even more hardcore option of digging up the payloads embedded in the...
  20. I

    How to find the Braking Torque of an Eddy Current Braking Setup?

    Homework Statement: Finding the braking torque applied on a moving disk as a result of the Eddy Currents Homework Equations: $$F = \sigma v V B^2$$ So right, Basically my problem is how to find the torque exerted by an eddy current braking setup. My setup consists of a disk rotating on an...
  21. dvscrobe

    Engineering Reverse Current PMDC Motor Braking Using Power Electronics

    Summary: How do you determine the armature current during the braking time? For a simple permanent magnet DC motor with a known resistance and inductance in series with the armature, I would like to know how to determine the armature current if there was an electronic motor drive controlling...
  22. D

    Kinematics problem: Determine the velocity of this car during braking

    Step 1. Integrate the function --> it comes out to -1.8t3+t2-8t+c Step 2. Figure out the integration constant --> I know that the velocity of the car is 30m/s at t=0s so making 30m/s = -1.8(0s)3+(0s)2-8(0s)+C it would seem that C is 30m/s Step 3. Calculate velocity at 4s --> V(4s)=...
  23. H

    Tension in a Rope from Lowering Down and Friction Braking Torque at Stop

    (The weight scale = 10 kg). After initial force, now the mass is lowering down at constant speed of 1 m/s. The motor with pulley's radius of 1 meter is exerted 100 Newton m to keep constant V. The motor speed is about 9.55 rpm. * All other weights, inertia and frictions of the system is...
  24. billiards_guy

    Automotive Braking with one caliper out of four

    I debated with a friend tonight, and I need some unbiased input. We were talking with a 3rd party that states that they only have one *working* brake caliper, of four. Assertion #1. (Basic four wheeled vehicle) 3rd party also states that there is no correction in steering needed, when...
  25. A

    Is Electromagnetic Braking Suitable for High-Speed Monorail Stopping?

    I'm working on a project and came across electromagnetic braking recently and I'm really curious to know if it's really feasible. The project in brief is a vehicle on a monorail at speeds of +600km/hr needs to be stopped. The monorail is made of an alloy of aluminium. I have no background in...
  26. RedBaron

    Capacitors and regenerative braking

    So I'm interested in adding a bank of capacitors to help reduce the initial load on my batteries when accelerating from a stop but my current set up uses regenerative braking. My electrinics are this order, Motors, VESC, BMS, 10s5p Li-ion pack. If I add capacitors between the bms and vesc to...
  27. F

    Bremstrahlung Braking radiation spectra expected and total power

    as homework, I have to do the following exercise: Bremstrahlung emission : We are interested in ionized plasma of density ##n##, at temperature ##T## with ions of charge number ##Z##. 1. Explain the physical origin of bremstrahlung radiation 2. Represent the expected spectra (shape and...
  28. A

    "How far did the car move while braking?"

    Homework Statement :[/B] A ball rolls onto the path of your car as you drive down a quiet neighborhood street. To avoid hitting the child that runs to retrieve the ball, you apply your brakes for 1.06 s. The car slows down from 14.5î + 4.50 m/s to 8.25î + 3.50 m/s. How far did the car move...
  29. E

    Help with a car under braking and friction force

    Got a question for you mechanics enthusiasts out there. Here https://i.imgur.com/Px0Hakg.jpg from what I gather is a basic force diagram depicting a car accelerating along a straight road, Dr represents the driving force of the engine, Fr the friction acting on the tyres against the direction of...
  30. C

    Motion problem: motorist's braking time including reaction time

    Homework Statement A motorist is traveling at 10m/s in a car whose maximum deceleration rate is 5.0 m/s^2 The effective reaction time between seeing a hazard and starting to brake is 0.5s Calculate the thinking distance for the drover ar this speed (ie the distance traveled during his...
  31. Z

    Kinematics Problem: Train braking and blocking an intersection

    Homework Statement A train 400 m long is moving on a straight track with a speed of 21.6m/s. The engineer applies the brakes at a crossing, and later the last car passes the crossing with a speed of 5.0m/s. Assuming constant acceleration, determine how long the train blocked the crossing...
  32. baldbrain

    Reaction time while stopping a car

    Homework Statement To stop a car, first you require a certain reaction time to begin braking; then the car slows down under constant breaking decelaration. Suppose that the total distance moved by the car during these two phases is 56.7 m when its initial speed was 80.5 km/h and 24.4 m when its...
  33. hugo_faurand

    Car's braking distance formula

    Hello everyone ! I'm working on my highway code and my book give me the approximate formula and the real formula of the braking distance. Here's the real formula according to the book : $$ Bd = \frac{V^2}{254 \times f} $$ With : V : the velocity f : the adherence coefficient. But I have on...
  34. Gyro de Pyro

    Magnetic plate eddy current braking effect on a copper disc

    Hi, I've seen many videos of neodymium magnets sliding slowly down an inclined copper plate, or slowly down a copper tube - due to eddy current braking,but never the other way around. My question is; will a copper disc sliding down an inclined magnetic plate, or down a magnetic tube act in the...
  35. Muhammad Danish

    Relationship between Velocity and Acceleration

    When the driver applies brakes its velocity starts decreasing and direction of acceleration will be same to the direction of velocity. Is this statement True of False? Please explain the true concept of this scenario. As far as I understand is that Velocity will start decreasing. But I am...
  36. cosmik debris

    Automotive How is variable engine braking implemented in a vehicle ECU?

    Hi All, The ECU on my motor bike allows you to select different amounts of engine braking in it's various riding modes. I imagine that the ECU just opens up the throttle bodies a little so that at closed throttle the engine still delivers a bit of torque. Doing this will increase the idle speed...
  37. Michael Sofroniou

    Braking Force from Eddy Currents on a Rotating Disk

    Hello! I'm currently working on a project that will utilize the phenomena of eddy currents to apply a braking force to a rotating disk. Some background on this project: My team was tasked to create a physical therapy training device to train patients in wheelchair propulsion at resistances lower...
  38. G

    Braking force required on the disc brake pads

    Hello, I'm currently working on the design of an e-caliper and I need to this effect to determine the linear force at which the pads have to be pressed against the disc to slow down a car swiftly. The result of my calculations is that the pad of a single front brake has to be pushed with a...
  39. physea

    Is it possible to know if a vehicle is braking?

    Hello! How can we identify that a car is braking, just by accessing its wheels? I think dynos work like that? Ie they can tell if the torque is negative or positive by touching the spinning wheel? Any hint?
  40. J

    Torque produced by friction when braking in a car

    Hi So I am busy studying rotational motion and there's an example in the book where they explain that when a car brakes the force of friction acts as a torque force which explains why a car lifts up at the back when braking. Because the car does no rotational motion they say the net torque is...
  41. B

    What Is the Frequency of Radiation Emitted by a Constantly Accelerating Charge?

    When a charge is accelerated it brakes because it emits radiation. If a carge is accelerated with costant acceleration and the traiectory is a line what is the frequency of the emitted radiation? (I think 0Hz but i am not sure)
  42. T

    What forces oppose a car's motion when braking?

    I understand intuitively that an automobile is set in motion because the wheels apply a force on the road in a backwards direction. Using Newton's 3rd law, the car gets propelled because the road applies a reaction force in the opposite direction. Before starting to ask my full question, I...
  43. T

    Automotive Why does automatic emergency braking not work in all speeds?

    Adaptive/active/radar cruise control (Update: It is not adaptive cruise control. It is automatic emergency braking) works only at or below 50 miles (per hour) in some high end cars like range rover, and even below that in other cars. Does anyone know why?Thanks a lot
  44. Poetria

    Relative velocities: braking car

    Homework Statement A bicycle rider is riding at a constant speed of v(b) and at t=0 is 17m behind the car. The cyclist reaches the car when the car just comes to rest. The car is moving with an acceleration:for 0<t<t(1) a(c)=0 for t(1)<t<t(2) a(c)= -c(t-t(1)) where its initial component...
  45. Bill_Nye_Fan

    Finding the Braking Force of a Truck on an Inclined Plane

    Homework Statement A truck of mass 1.5 tonnes (1500 kg) is moving at a speed of 36 km/h down a hill of slope 1 in 6. The driver applies the breaks and the truck comes to rest after 2 seconds. Find the breaking force, which is assumed to be constant, ignoring any other resistant forces...
  46. G

    A Does Magnetic Braking Theory hold up?

    Magnetic braking is a theory explains the loss of stellar angular momentum and is used extensively to describe the given rotation stars. However, on a smaller and more directly observable level, when we consider Jupiter's rapid rotation rate of less than ten hours and its accompanying powerful...
  47. T

    The physics of braking on a motorcycle (manual transmission)

    When trying to abruptly stop a motorcycle that is in motion, can engine braking actually have a negative effect on the rate of deceleration? Scenario: a motorcycle is traveling down a straight highway at 100mph in 6th gear and needs to perform an emergency stop. The weather is clear and road...
  48. cnh1995

    Zero sequence braking of induction motor

    I recently read about zero sequence braking of induction motor. In zero sequence braking of induction motor, the stator phases are connected in series and a single phase ac supply is connected across the series combination. Thus, the currents in all three phases are co-phasal, which are called...
  49. C

    Traction question -- Best braking strategy in snow and ice

    When driving on snow and ice does engine braking (by downshifting) provide more traction than applying brakes in a slow and controlled manner?
  50. TheChemist_

    How can Superman minimize the braking distance?

    Homework Statement So here is the Problem: A big truck (m=50t) is going at 100km/h. Now the truck can't brake anymore and Superman comes to aid. He (has a mass of m=100kg) tries to stop the truck while he is wearing shoes with a rubber-texture and a friction coefficient of µ = 0.8. Assume that...