Constant speed Definition and 135 Threads

In everyday use and in kinematics, the speed (commonly referred to as v) of an object is the magnitude of the rate of change of its position with time or the magnitude of the change of its position per unit of time; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero.
Speed has the dimensions of distance divided by time. The SI unit of speed is the metre per second (m/s), but the most common unit of speed in everyday usage is the kilometre per hour (km/h) or, in the US and the UK, miles per hour (mph). For air and marine travel the knot is commonly used.
The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in a vacuum c = 299792458 metres per second (approximately 1079000000 km/h or 671000000 mph). Matter cannot quite reach the speed of light, as this would require an infinite amount of energy. In relativity physics, the concept of rapidity replaces the classical idea of speed.

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  1. N

    Understanding Light Speed: The Impact of an Observer Moving at 10% C

    An observer is moving at 10% the speed of light. A light ray whizzes past him. He measures its speed to be exactly 186000 miles/sec. What happens at the physical level that he does not measure the speed of light to be less? Has the time of the observer slowed down? Or what?
  2. A

    What Is the Maximum Constant Speed of a Motorcyclist on a Curved Path?

    Homework Statement A motorcyclist travels around a curved path that has a radius of 450 ft. While traveling around the curved path, the motorcyclist increases speed by 1.10\frac{ft}{s}. Determine the maximum constant speed of the motorcyclist when the maximum acceleration is 7.00...
  3. B

    Vector Proof Of Constant Speed Means Perpendicular Acceleration.

    Homework Statement Prove that when speed is constant that V(T), and A(T) are perpendicular. Homework Equations I know this involves the dot product to show that the dot product of the vectors is zero. The Attempt at a Solution In my head I thought that since the speed is...
  4. S

    Discovering Constant Speed in Bosun's Chair Problem: Mechanics and Techniques

    Homework Statement In a typical bosun's chair problem (in which an individual is on a platform suspended in the air by a massless, frictionless rope- about a pulley- holding the opposite end of the rope) one asks what pulling force is required to set the bosun chair (and person) into movement at...
  5. W

    Finding Force of an Object on Incline w/ Constant Speed & Coefficient

    Homework Statement Hi guys and gals, Having an issue with this one and was hoping to get some help. I'm going to write out the equation and include an attachment with my free body diagram. Q: How long a force parallel to a 20° hill does it take to push a 100-lb box up the hill at a...
  6. S

    Plot motion of particle with constant speed and angular velocity

    Consider the problem of a particle sliding inwards with a constant speed c and starting at radius R=pc/Ω, on a platform rotating with a constant angular velocity Ω. Give a plot of the trajectory of the particle from r=R to r=0, for p=0.5, 1, 2, 6. I'm a little confused on how to do this...
  7. L

    Equilibrium of a constant speed

    Homework Statement The model airplane in Figure 5.6 has a mass of 0.90 kg and moves at a constant speed on a circle that is parallel to the ground. The path of the airplane and its guideline lie in the same horizontal plane, because the weight of the plane is balanced by the lift generated...
  8. S

    DC motor turning at constant speed eventually

    Hi, I have a question related to the DC motor that i hope you geniuses can help me with. By Fleming's Left hand rule, there is an induced forced (IF in diagram) at the downwards position at the armature AB. Thus, by Fleming's Right hand rule there is an induced current (IC in diagram) which...
  9. H

    Is Constant Speed Equal to Acceleration?

    A car moving with a constant speed of 20m/s is said to have undergone an acceleration. Is this possible? A. yes because the car can be going around a corner B. no because constant speed means there is no acceleration C. yes because the direction of the car is also constant D. no because no time...
  10. C

    Understanding Relativity: The Constant Speed of Light Phenomenon

    Relativity says that the speed of light is constant for all observers regardless of their state of motion. So does that mean even if you are heading towards a light beam at a constant velocity that the light beam would take the same amount of time to reach you as when you are at rest relative...
  11. B

    Work and Constant Speed: Exploring Kinetic Energy

    I am reading this article on the concept of work,http://www.lightandmatter.com/html_books/lm/ch13/ch13.html#fig:tractor-pulling-plow , but the paragraph immediately below the section "Calculating work as force multiplied by distance" appears to implicitly say that some sort of work is being...
  12. N

    A person pushes a 10.0 kg lawn mower at constant speed with a force of

    A person pushes a 10.0 kg lawn mower at constant speed with a force of 82.0 N directed along the handle, which is at an angle of θ = 45.0° to the horizontal (Fig. 4-45). (b) Calculate the horizontal retarding force on the mower (c) Calculate the normal force exerted vertically upward on the...
  13. R

    Understanding Time Dilation: Explaining the Constant Speed of Light

    I've read that time and space dilate under acceleration to ensure the constant speed of light. I'm having trouble visualizing a scenario that illustrates this concept. Could someone please explain this to me? Thanks.
  14. E

    Wire moving at constant speed in a magnetic field

    So let's say I have a wire of length l moving in a uniform magnetic field of constant velocity. Now the induced EMF = Blv Constant velocity implies constant EMF generated per unit time. I even have a graph of EMF vs time in my textbook for such a situation showing a flat horizontal line...
  15. J

    Power concept related to gravity, constant speed, and air resistance

    Homework Statement An object weighting 100N is traveling vertically upward from the Earth in the absence of air resistance at a constant velocity of 5 m/s. What is the power required to keep the object in motion? Homework Equations P = ΔE/t and P = Fvcosθ The Attempt at a Solution...
  16. D

    HELP determine work needed to push a crate up a ramp at constant speed

    Homework Statement A ramp leading up to a loading platform is 3 m long and 1 m high at its highest point. If the friction is ignored, what work is needed to slide a 600-kg crate up the ramp at a constant speed? a) 2.00 *10^2 J b) 5.89 *10^2 J c) 1.80 *10^3 J d) 5.88 *10^3 J I...
  17. A

    How does an object maintain circular motion at constant speed without spiralling

    I saw this interesting question on Y/A http://answers.yahoo.com/question/index;_ylt=AkFE6dXbkK3rT4.lc.Hete7sy6IX;_ylv=3?qid=20120314045354AAn4O3N If an object in circular motion is being constantly accelerated toward the centre of a circle, why doesn't its velocity (vector) inward to the...
  18. K

    Magnitude of object with constant speed

    Homework Statement in the physics laboratory experiment, a 6 kg box is pushed across a flat table by horizontal force F. if the box is moving at a constant speed of 0.35 m/s and the coefficient of kinetic friction is 0.12. what is the magnitude of F. Homework Equations F=μ*Fn where F...
  19. K

    Crate on a frictionless ramp, constant speed.

    Homework Statement A 130 kg crate is pushed at constant speed up the frictionless 23° ramp shown in the figure. What horizontal force F is required? Homework Equations F=ma F(parallel)=mgsin(theta) F(perpendicular)=mgcos(theta) The Attempt at a Solution I know that because it...
  20. D

    Power needed to climb constant slope at constant speed

    i failed science at school and often want answers to q's thank God for pf! i want a nice easy way to work out how much power you would need to climb hills: power versus weight and gradient is what I am after. assume constant speed constant gradient ignore wind resistance. I am after simple ball...
  21. rcgldr

    Parabolic path at constant speed

    parabolic path at constant speed? (having issues) I found a brief mention of this problem at a few web sites. An object follows a parabolic path at constant speed. I'm having some issues with the math involved: Assume the path is defined by y = 1/2 x2, and that the constant speed is c...
  22. A

    Pulleys moving down with constant speed

    Homework Statement Please refer diagram attached. The pulleys are moving down with constant speed u each. Pulleys are light , string ideal. What is the speed with the mass moves up? Homework Equations The Attempt at a Solution Now, I got the answer as ucosΘ, obviously...
  23. M

    Carousel physics. Calculating constant speed and distance.

    Homework Statement A child a rides a carousel at t = 0 and moves in a circle that is 8 m in circumference at a speed of constant modulus of 1m / s. determine: a) the movement of t = 0s to t = 1s b) the average speed from t = 0s to t = 3s c) the average acceleration between 1s and 3s...
  24. V

    Is a constant velocity the most efficient way to drive a car?

    I've read (I think it was on slashdot) that using constant velocity cruise control on your car is much more energy efficient than letting your speed vary. To the point where they said you would want to control your speed to much less than 1 kph. What is the general consensus on this? I'm a...
  25. J

    Finding thickness of paper based on rate of change of radius and constant speed

    I need find the thickness of a piece of paper based on the known linear speed of the paper coming off the roll and the change in diameter of the roll. I have the ability to see the linear speed. It is consistant but changes from roll to roll. I know the starting radius, instantaneous radius...
  26. F

    Chair-lift at constant speed: confusion over passengers per minute, power, etc.

    Homework Statement A chair-lift runs at constant speed. Each passenger starts from rest at the lower station, and is delivered to the upper station with the speed of the lift. The lift raises 30 passengers a minute, of average mass 75 kg. The top of the lift is 300 metres higher than the...
  27. E

    Does the particle have constant speed? If so, what is it constant speed?

    Homework Statement Each of the following equations in parts (a)-(e) describes the motion of a particle having the same path, namely the unit circle x2 + y2= 1. Although the path of each particle in part (a)-(e) is the same, the behavior, or "dynamics," of each particle is different. For each...
  28. A

    Constant speed and deaccelaration

    Homework Statement R is traveling in a car at a constant speed of 18ms when she suddenly breaks. if reaction time is .52s for applying foot to break how far is traveled before break is applied? and if the break cause a deceleration of 5m/ssquared, how is traveled before stopping?
  29. T

    Constant speed vs. repeated acceleration

    Assuming only air friction, do you think it is equally as energy efficient to reach a destination in a vehicle traveling a constant 60 MPH as it is to reach that destination through repeated accelerating to 60 MPH and allowing the vehicle to coast to a stop? That is, you accelerate to 60, then...
  30. alyafey22

    Constant speed and acceleration.

    As we know that an object can move with constant speed and accelerate this can be expressed with an object moving along a curved path with constant speed ,hence it has an acceleration ... my question is how an object can have an acceleration and at the same time is moving with constant speed ...
  31. I

    The Constant Speed of Free Falling Objects

    When an object free falls, its accerleration is constant, but does its speed change? If so is it practicing uniform or non uniform motion?
  32. D

    Maximizing Distance for Clowns Shot from a Cannon

    In a circus act, clowns are shot from a cannon at a constant speed vo = 11.7 m/s. The angle of launch may be varied. a. What is the maximum distance D that a clown may travel, if the landing pad is at the same height as the mouth of the cannon? b. The circus master wants to shoot two...
  33. S

    How can something have both a constant speed and a precise location?

    How can something that moves at a constant speed for all reference frames have a specific location? Suppose two observers Alice and Bob are in motion with respect to each other so that they do not have a common inertial frame. But when both of them measure the speed of a photon, they find it...
  34. G

    Why Is the Constant Speed of an Elevator Ignored in a Free Fall Calculation?

    While riding on an elevator descending with a constant speed of 3.0 m/s, you accidentally drop a book from under your arm. How long does it take for the book to reach the elevator floor, 1.2 m below your arm? What is the book’s speed when it hits the elevator floor?My question is why is 3.0 m/s...
  35. J

    Tape experiment how to pull at constant speed?

    hi all i'm a high school student doing a physics experiment about the peeling force of a tape. I want to see the realtionship between the peeling force and the peeling velocity but I cannot think of a good way to pull at constant speed. I tried to connect the spring to a motor so that the...
  36. F

    What is the relationship between constant speed rolling motion and friction?

    hi ,this is my first post (and its not HW) i currently study dynamics of rigid bodies using (Hibbeler) and there's one thing about this type of motion (rolling) that just seems to elude me for any planar motion we have 3 equations \Sigma F_{{x}}={\it ma}_{{g_{{x}}}} \Sigma F_{{y}}={\it...
  37. M

    Calculating Constant speed of an Elevator Rising

    Homework Statement The motor for an elevator can produce 14kW of power. The elevator has a mass of 1100 kg, including its contents. At what constant speed will the elevator rise? Homework Equations I'm not really sure. Probably Gravitational potential = mgh. Kinetic energy = 1/2mv^2...
  38. D

    Find constant speed using mass and power

    Find constant speed using mass and power [SOLVED] Homework Statement A 613.0 kg mass is placed on a forklift that can generate 950 W of power. What is the constant speed of the forklift while lifting this load? Homework Equations P = W/▲t W=Fapp*▲d Fg=mg The Attempt at a...
  39. 1

    Light's constant speed and frames of reference

    Been reading up on physics out of pure interest, just learning really. Mainly started special relativity and learning about the inertial frames of reference. I think I understand that, but here's what I don't get. If from one inertial frame of reference moving at a constant 100 MPH, I toss...
  40. R

    Exploring the Universal Constant of Light Beyond Maxwell's Equation

    hi all, this is a very basic question. apart from maxwell's equation, why else is the speed of light a universal constant?
  41. D

    Astronaut traveling at constant speed, throws a wrench

    1)Homework Statement An astronaut of mass 82.0 kg is taking a space walk to work on the International Space Station. Because of a malfunction with the booster rockets on his spacesuit, he finds himself drifting away from the station with a constant speed of 0.600 m/s. With the booster rockets...
  42. P

    Force On Object With Constant Speed

    A sack of flour of mass 6.00 kg is lifted vertically at a constant speed of 4.00 m/s through a height of 18.0 m How great a force is required? F=ma I found the force that the sack has on the Earth (58.8N), but don't understand how I am suppose to find what force is being applied to...
  43. O

    Unknown distances, constant speed, average velocity

    Homework Statement A car travels along a straight line at a constant speed of 48.5 mi/h for distance d and then another distance d in the same direction at another constant speed. The average velocity for the entire trip is 30.5mi/h. a) What is the constant speed with which the car moved...
  44. L

    Motion Equation with constant speed (Time sensitive )

    Motion Equation with constant speed (Time sensitive!) Homework Statement A stone thrown horizontally from a height of 6.02m hits the ground at a distance of 12.90m. The initial speed is 11.64 m/s. Calculate the speed of the stone as it hits the ground. Neglect air resistance. Homework...
  45. I

    Need Help with problems involving constant acceleration and constant speed. :/

    Homework Statement At the instant the traffic light turns green, a car that has been waiting at an intersection starts ahead with a constant acceleration of 3.60 m/s^2. At the same instant a truck, traveling with a constant speed of 20.5 m/s, overtakes and passes the car. How far beyond its...
  46. M

    Why does an object have constant speed with Centripetal Force

    Hi, I understand how centripetal force works and all. But I still don't understand, when looking at a satellite orbiting the Earth, the only force acting is its weight, which is in the direction of the Earth. How does its circular motion start in the first place? If the only force there is is...
  47. O

    Wire Apparatus that Moves with Constant Speed Under Weight

    Ok, here's a description of what I'm trying to achieve. I want to design a wire apparatus that lowers a weight using the mass of the weight as the force, but then somehow achieves a balance of forces when the velocity reaches 1 m/s. This is simple enough using friction (I think), but the problem...
  48. S

    Object w/ Constant Speed Doesn't Lose KE Faced w/ Resistance

    Hello, "Potential Energy (PE) + Kinetic Energy (KE) = Total Energy When air travels through an airway at a CONSTANT FLOW RATE, the total energy of the fluid (PE + KE) decreases because friction converts some of this energy into heat. Since the fluid is moving at a constant flow rate, the...
  49. O

    Move a Part at Constant Speed Under its Own Weight

    How can I make a hanging weight attached to a wire move at a constant speed under its own weight? The mass of the weight may vary and is not known beforehand.
  50. J

    Blocks moving on frictionless incline at constant speed, accleration

    Homework Statement There is no friction Part A) Find the mass of block C so that block B moves up the incline with a constant speed Part B) fint he mass of block C so that Block B moves up the incline with a constant accleration a = g/2 Homework Equations The Attempt at a...
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