What is Velocity: Definition and 1000 Discussions

The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time. Velocity is equivalent to a specification of an object's speed and direction of motion (e.g. 60 km/h to the north). Velocity is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of bodies.
Velocity is a physical vector quantity; both magnitude and direction are needed to define it. The scalar absolute value (magnitude) of velocity is called speed, being a coherent derived unit whose quantity is measured in the SI (metric system) as metres per second (m/s or m⋅s−1). For example, "5 metres per second" is a scalar, whereas "5 metres per second east" is a vector. If there is a change in speed, direction or both, then the object has a changing velocity and is said to be undergoing an acceleration.

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  1. Like Tony Stark

    Finding angular velocity for a rope to be cut

    I wrote Newton's equations for each body (I took ##x## as the axis aligned with the tension) ##m_1##: ##x)f*_1 -T_1+T_2=0## Where ##f*_1=\omega ^2 r_1## ##m_2## ##x)f*_2 -T_2=0## ##x)f*_2=T_2## Where ##f*_2=\omega ^2 r_2## I wrote that ##T_2=1100 N## and solved for ##\omega##, and I got...
  2. Like Tony Stark

    Finding the angular velocity of a rotating arm

    A) The slider experiments three forces, all of them are on the ##x## axis (considering ##x## axis as the axis aligned with the arm): Normal force (exerted by the support), elastic force and centrifugal force, which is ##m.(\omega^2 r)## Elastic force is equal to ##Fe=-k \delta =-2 (R-2R)=2R##...
  3. M

    Α baseball player throws the ball....

    Hi all ! I wonder if I'm right. (From : Fundamental University Physics, Volume 1 (Mechanics) - (Marcelo Alonso, Edward J.finn) Addison Wesley 1967) This is my try: * I have the Greek version of the book and there is no answer.Thanks.
  4. K

    Closest approach from initial velocity and impact parameter

    Here were my assumptions: Energy and angular momentum are both conserved because the only force acting here is a central force. The initial angular momentum of this particle is ##L = mv_0b## and we can treat E as a constant in the homework equation given above. I solved for the KE (1/2 mv^2) in...
  5. Alexandra Fabiello

    Finding distance east given west dist., velocities, and average velocity

    6.44 km * 1000 = 6440 m/2.51 m/s = 2565.737052 s = west time av = (6440 m + - east distance)/(2565.737052 s + east time) 2565.737052 s + east time = total time 1.28 m/s * total time = (6440 m) - (0.495 m/s * east time) 1.28 m/s * (2565.737052 s + east time) = (6440 m) - (0.495 m/s * east...
  6. Like Tony Stark

    Measuring position and velocity from a non inertial reference frame

    I) For ##A##, the positition is ##\vec r=(0;V_0 . t;0)##. For ##B##, we have ##\vec r_A=\vec r_B + \vec r_{A/B}##, but ##\vec r_{A/B}## is equal to zero because they have the same origin, so the position measured from ##A## is equal to the position measured from ##B## II) For ##A##, velocity...
  7. D

    B Is the Velocity of Electron Spin Calculable Using Classical Models?

    Addressing to electron as being rigid body that precesse is probably controversial. Are there any attempts to stick to that model and to calculate its quantize tangent velocity?
  8. D

    Unusual escape velocity derivation

    Is it possible to derive escape velocity say using momentum and force balance considerations? or using angular momentum consideration? Namely, any other approach then energy consideration that utilizes gravitation potential energy and kinetic energy?
  9. N

    Velocity of an object with varying mass

    I have tried several things but I am a little uncertain if I’m thinking right so a little hint goes a long way. I think I have to use the law of conservation of momentum as the collision between the raindrops and the box is inelastic. But I am unsure how to set up the equation.
  10. jisbon

    Finding angular velocity when the CM is directly below the pivot

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  11. S

    Coriolis force caused by tangential velocity

    From another recent thread I learned that you see a Coriolis force if an object in a rotating reference frame moves along a tangent at some velocity v. (I was already familiar with the case where the velocity is radial). I still find it a little counter-intuitive that the force has the same...
  12. jisbon

    Calculate the velocity of a cylinder as it leaves the top of a slope (using Energy)

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  13. jisbon

    Finding the launch velocity of a point charge in a e-field

    I'm not sure how to proceed with this, but here are my findings/hypothesis: First we find the electric field contributed by the plate with ##E=\frac{\lambda}{2\pi r\epsilon_{0}}## where r=2? After finding out the electric field, is it safe to assume I can find the acceleration of the point...
  14. A

    Ground Velocity: -269.6 km/h [N 5.6 E]

    The velocity of the plane relative to the ground is 269.6 km/h [N 5.6 E]. Shouldn't it be the velocity of the ground relative to the plane is - 269.6 km/h [N 5.6 E]
  15. jisbon

    Find the velocity of a point charge in a ring of electric field

    Okay, I am not even sure how to startr with this question. But here's my theory: First I will need to the electric field produced by the ring using the formula: ##E = k\frac{\lambda a}{(x^2+a^2)^{3/2}}## After finding out electric field produced by ring, am I supposed to find out the...
  16. zvjaginsevfan

    How to find the Acceleration when Velocity depends on position?

    This is a homework question from my friend, I found the time but a tough differential equation occurred when I was trying to find accelaration, is there a simple solution for this?
  17. Like Tony Stark

    Measuring position, velocity and acceleration in relative motion

    Well, ##r(t)## in ##A## is just a vector ##(0;y)## because is tangent to the trajectory. Then, from the perspective of ##B## the particle moves in an uniform circular motion. Is this right? The velocity from ##B## must be ##\omega##, right? And what about acceleration?
  18. S

    Is the Elastic Collision Equation Applicable in This Mechanics Scenario?

    So, I understand that there are 2 objects, so is the equation we are supposed to use is the elastic collision equation, right? I just need help getting started, thank you.
  19. Yalanhar

    Minimum velocity to throw a object to another planet

    So I integrated the work done on the object by both planets. Work1 is until x, and Work2 is from x to d. Where x is the point where both gravitational forces are equal. ##W_1=\int_0^x \frac{GMm}{r^2}dr - \int_0^x \frac{GMm}{(3R+D-r)^2}dr ## ##W_2=\int_x^D \frac{GMm}{(3R+D-r)^2}dr - \int_x^D...
  20. G

    Acceleration and Displacement from a Velocity vs. Time Graph

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  21. B

    Distance Velocity Graph: What Does the Area Represent?

    Summary: Gradient = Acceleration(?) Area = Time (?) Good evening, I have a problem that presents itself in a distance (y) velocity (x) graph. I've never come across this, and in my Physics textbook, the section dedicated to graphs does not have it. My question is, what does the area of the...
  22. L

    Average velocity and instantaneous velocity

  23. Like Tony Stark

    Calculating the radius of curvature given acceleration and velocity

    Well, what I've done so far is calculating the magnitude of velocity and acceleration replacing ##t=2## in ##\theta (t)## and ##r(t)## so I could get the expressions for ##\dot r##, ##\dot \theta##, ##\ddot r## and ##\ddot \theta##. But that's not my problem... my problem is related to the...
  24. Like Tony Stark

    Decomposing velocity vectors into polar axis

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  25. PainterGuy

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  26. K

    Velocity Map Imaging: Understanding 3D Reconstruction

    Hello! I am a bit confused about the image reconstruction for velocity map imaging. As far as I understand, at the interaction point, ions are produced in a Newton sphere which gets projected on a 2D screen (such that all the particles with the save velocity get mapped on the same point). What...
  27. Abhimessi10

    Engineering Houston's piezoelectric method for finding the velocity of light

    Crystal acts as a diffraction grating.Although I don't know what that means.
  28. karush

    MHB 4.1.26 graph of velocity over acceleration graph

    ok not finding this easy but the red is mine drawn over the given book graph also want to convert the whole thing to tikx graph
  29. M

    Zero Friction on the Moon: Driving at Constant Velocity Without Air Resistance

    Suppose we are driving on moon (I mean there is not air resistance) at a constant velocity. Suddenly the car goes on an icy land (the friction is zero). What happens? In other words, if we drive at constant velocity and there isn't air resistance, Is there any friction force between tires and...
  30. jisbon

    Relative velocity of a ball thrown inside a moving truck

    Hi all, Not sure on how to start this question in the first place, but from what I gathered from the data given I managed to derive this from the question: ##\theta = 53.13\deg## Let inside truck be t, final position be f, and ground be g ##D_{ft} = L## ##D_{fg} = xL## Also, for velocity...
  31. E

    Relative velocity of two gravitationally attracting spheres

    There have been some other threads on similar problems but none address one specific point I'm confused about. The change in GPE of a body is the negative of the work done on that body by a gravitational field between two points; by this logic, since the same (but opposite) gravitational forces...
  32. Seth Greenberg

    What is the angular velocity in the center of a rotating disc?

    I have a disc. The center of the disc is its center of mass and the motion of the disc is purely rotational (no translation). What is the angular velocity in the center of the rotating disc?
  33. Prabs3257

    Velocity of the center of mass in constrained motion

    I tried getting the velocity of a which by using constraint came out to be 3 and by using the eqn for vcom i got the ans as 3.5 i just want to confirm is this the correct answer
  34. jisbon

    Circular motion -- Find the angular velocity at t=3

    Hi everyone. Do correct me if I am thinking wrongly. So to find angular velocity, won't I just have to integrate angular acc = 2t, which means angular velocity = t^2? Hence, won't the answer be 3^2=9? The answer seems to be 5.43 :/ Thanks
  35. D

    Instantaneous versus average velocity?

    I have a hard time understanding what this problem even means. So I can't even begin with it.
  36. karush

    MHB Cp2.63 find the initial velocity

    cp2.63. The acceleration of a particle is given by $$a(t)=-2.00 \, m/s^2 +3.00 \, m/s^3.$$ a. find the initial velocity $v_0$ such that the particle will have the same x-coordinate at $t=4.00\, s$ as it had at $t=0$. b. What will be the velocity at $t=4.00 s$ ok sorry but I don't even know...
  37. karush

    MHB 214 AP Calculus Exam velocity

    $\tiny{207 \quad DOY}$ A particle moves along the x-axis. The velocity of the particle at time t is $6t - t^2$. What is the total distance traveled by the particle from time $t = 0$ to $t = 3$ ? $(A)\,3 \quad (B)\,6 \quad (C)\,9 \quad (D)\,18\quad (E) \, 27$ ok think this is correct...
  38. Shivam

    Calculating Safe Velocity: Why Is 4th Option Incorrect?

    1). I calculated maximum safe velocity using the equation - V(max)=√200x10x0.2 =20m/s So the speed at which car is traveling is greater than the safe speed.. So the car should skid. So why 4th option is not correct ?
  39. S

    Relation between mass distribution and angular velocity

    Is E the correct answer because I think angular velocity is independent of mass distribution of the object? Thanks
  40. G

    Determination of the velocity of a particle in a hollow cone

    Hi, please could I ask for help with the following question: A smooth hollow circular cone of semi-angle α, is fixed with its axis vertical and its vertex A downwards. A particle P, of mass m, moving with constant speed V, decribes a horizontal circle on the inner surface of the cone in a plane...
  41. Adesh

    A question of kinematics involving a changing velocity vector

    The statement "at the initial moment of time v ⊥ u and the points are separated by a distance l " gives us a picture like the one which I have added in attachment. As the time passes velocity vector v would gradually change from fully vertical to fully horizontal in order to meet point B. Now...
  42. PainterGuy

    Equalization of velocity components and momentum conservation

    Hi, I understand and I'm sorry that there are going to be many loopholes in what I'm trying to put together and that too without any mathematical formulation but I don't even know where and what to start with. Suppose we have a finite length insulated hollow cylinder filled with with air at 1...
  43. P

    Why is the Lorentz force linear with velocity?

    I am working on derivation of Lorentz force. (I know that Lorentz force is in some sense definition of fields, but still there is nontrivial dependence on velocity). I want to derive that the force is linear in components of velocity, so for example $$F_x=q(E+Av_x + Bv_y + Cv_z ),$$where ##A...
  44. A

    Velocity Question for a Car Accelerating Down a Road

    240/8=30.
  45. karush

    MHB 4-39 magnitude of its velocity after falling 10.0m

    a) what is its speed after falling to 2.00s motion formula $v=u+at$ so $v = 6.00 \dfrac{m}{s} + 9.81 \dfrac{m}{s^{\cancel{2}}}{2.00 \cancel{s}} = 27.6 \dfrac{m}{s}$ b) How far does it fall in 2.00s distance formula $d= ut + \dfrac{1}{2}at^2$ so...
  46. karush

    MHB 2.6 Calculate the average velocity of the car in different time interval

    OK I just had time to post and hopefully ok but still typos maybe the graph was done in Deimos wanted to try tikx but not sure about the polynomial trying to as many physics homework before classes start on Aug 26 Mahalo
  47. G

    Calculation of minimum angular velocity of a mass on a spinning plate

    Problem Statement: How to calculate minumum angular velocity of a mass on a spinning plate Relevant Equations: f=mrw^2 Hi, here's the question: a) A rough horizontal plate rotates with a constant angular velocity of w about a fixed vertical axis. A particle of mass m lies on the plate at a...
  48. samm12345

    What is the final angular velocity of each cylinder

    Problem Statement: The uniform 4-kg cylinder A, of radius r = 150 mm, has an angular velocity w = 50 rad/s when it is brought into contact with an identical cylinder B which is at rest. The coefficient of kinetic friction at the contact point D is uk. After a period of slipping, the cylinders...
  49. M

    I Velocity Addition: Angled Motion Explained

    Any ideas?
  50. Manasan3010

    Impossible Relative Velocity Values

    The answers were 1) 150 km/h 2) 200 km/h 3 )500 km/h 4) 700 km/h 5) 800 km/h (Chosen Solution) I know that values 700km/h ,100km/h ,-100km/h are possible scenarios but in what ways are 150km/h ,200km/h and 500km/h possible ?
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