Kinematics Definition and 1000 Threads

  1. A

    I Please explain how length contraction and time dilation result in a constant c

    if light pulse is to the right, but moving car's velocity is to the left, we would expect c-v, but we get c instead which is greater. but if light pulse is to the right, and moving car's velocity is also to the right, we would expect c+v, but we get c instead which is smaller. how could the same...
  2. Patrick Herp

    Calculating the time needed until a known velocity for a vehicle with friction as a function of velocity

    The solutions for (a) and (b) are pretty straightforward, which I got 13 kW and 225 kW each, but when I try to solve for (c), I get stuck with this: $$ \begin{align} a &= \frac{F}{m} \nonumber\\ &= \frac{F_\text{max}-f(v)}{m} \nonumber\\ &= \frac{7(30)+6(30)^2 -70v-6v^2}{1.000} \nonumber\\...
  3. M

    Projectile motion with ##N## bounces on the ground

    Imagine we kick the ball from point ##\text{A}## with horizontal speed ##u_x^{\text{initial, A}} = v \cos \alpha## and vertical speed ##u_y^{\text{initial, A}} = v \sin \alpha##. The gravitational acceleration is ##\vec g##, the x-axis points towards the wall, the y-axis points upwards. The...
  4. whatever itis

    Trajectory of a particle in polar coordinates

    I tried using the formula for acceleration in polar coordinates, but I don't know how to solve the differential equations. How do I solve them? Is there a simpler way to do the problem?
  5. anthraxiom

    Calculating velocity of a particle if distances are constant

    I tried to solve using trigonometry. Let angle between line CA ad BA be theta and angle between BA and AC be alpha. 30sin theta= 40 sin alpha 30 cos theta + 40 cos alpha + 2vt=50 I have no idea how to proceed after this.
  6. paulb203

    Momentum: why don't the two carts become one?

    So far I’ve dealt with scenarios in which the vehicle colliding with the rear of the other vehicle ‘joins’ the other vehicle, and the ‘two become one’, so there is one final velocity. Why have these two vehicles not ‘become one’? I’ll have a go at the maths first then have a go at answering...
  7. C

    The problem of one tube and two balls on a plane

    none
  8. Z

    Robot and neural networks

    hello Take a 4 dof scara robot Calculate the x-y-z coordinates of the robot head , given the rotation angles of the 4 servo motors You can use the direct kinematics method Repeat this exercise a suitable number of times Train a neural net works of 3 neuron inputs (x,y,z) and 4 neurons outputs...
  9. E

    B Car spinning on a frictionless sheet of ice = absolute motion?

    Is this absolute motion ?
  10. Kalarudra

    I Help me to understand how integrating this function works

    Picture 1 Picture 2
  11. Bling Fizikst

    Kinematics in multiple frames

    We know $$\vec{v}_{B/O} \equiv \vec{v}_{B/1}$$ $$v_{O/F} = v\hat{e}_t$$ $$a_{O/F} = \dot{v}\hat{e}_t + \frac{v^2}{R} \hat{e}_n$$\$$\omega_{1/F} = -\omega \hat{j}$$ $$\omega_{2/1} = \dot{\theta} \hat{i}$$Using velocity transfer relations, $$v_{B/F} = v_{B/1} + v_{O/F} + \omega_{1/F} \times OB$$...
  12. Bling Fizikst

    Designing a speed bump given the maximum vertical wheel acceleration

    With the given information , we can find ##y=h\cos\frac{\pi x}{L}## Since , the wheel has constant velocity ##v## , we can write the $$\vec{a}=0\hat{e_t}+\frac{v^2}{\rho+r}\hat{e_n}$$ where $$\rho=\frac{\left[1+\frac{h^2 \pi^2}{L^2}\sin\frac{\pi x}{L}^2\right]^{\frac{3}{2}}}{\mid...
  13. Bling Fizikst

    Kinematics problem involving multiple frames

    So what i did was set up the cartesian axes ##e_1-e_2-e_3## and also the cylindrical ##e_r-e_\phi## The issue is how to calculate the cross products in the coriolis term without involving ##\phi##
  14. eddiezhang

    Time taken to slide down a circular path (with friction)

    This is for a math report that I'm supposed to write, which means I'm not supposed to use conservation of energy. This makes life much harder... so please bear with me. I am interested to see how you'd solve this purely kinematically though (if it can be solved that way). Please tell me if this...
  15. D

    B Acceleration as a function of position

    Why can't I simply integrate a(x)=m*x with respect to x to determine the speed of a particle as a function of position v(x)=1/2*m*x^2+A?
  16. Bling Fizikst

    Maximum tension in thread connecting loads

    Let's say the center of mass of the ring (wheel) moved a distance ##x##, tension in the thread connecting wheel and ##A## be ##T## and tension in the thread connecting ##A,B## be ##T'## : Due to no slip condition , ##a=R\alpha## where ##R## is the assumed radius of wheel Since ##P## is IAOR ...
  17. A

    Constant acceleration problem: Dog chasing a surprised cat

    Here I'm not worried about the solution as I got it. There are two ways I could come up with: Either finding the time it takes the cat to leap through the window, use that time to find what distance does the dog cross through the room Or: finding both times, for the dog and the cat to cross the...
  18. N

    Bead on a rod which is being pulled by an ideal string with velocity v

    I know That the velocity of each particle of the thread along the thread must be ##v_{0}## since the thread is inextensible. Now let's say the bead moves with some velocity ##v## For the particle attached to the bead to move with a velocity ##v_{0}## along the thread: ##v##cos##θ##= ##v_{0}##...
  19. T

    Engineering Time interval until a ball returns to its orign

    This is my solution below.
  20. Rick28

    Linear momentum but quadratic kinetic energy?

    no clues
  21. heyhey281

    B Quasistatic condition for a process involving a piston in a cylinder

    The time scale on which the change (such as a change in external parameters or a external parameters or an addition of heat) takes place is referred to as τ_exp. The relaxation time τ_relax, on the other hand, is the time that the system needs to return to a state of equilibrium after a sudden...
  22. J

    Confused about kinematic equations

    x=x0=vt v=v0+at x=x0+v0t+(1/2)at2 That (1/2) there does not make sense to me. It makes sense mathematically, if you integrate the velocity formula you get the (1/2) as a result of the integration rules and if you differentiate its needed to cancel out the 2 and arrive at the velocity...
  23. Old Man Scho

    B Tangential Velocity (maybe)

  24. SelzerRS

    Finding the intermediate height of a ball in terms of its maximum height

    Ive done this problem two different ways (sorry it’s messy) and keep getting hB = 1/9 hA, but my homework says it’s wrong. I’m guessing it’s because I assume that v0 is 0, but I’m not sure what other formulas or steps I need to take to either find or omit the variable. Are there any other...
  25. P

    I Solve equation from dimensional analysis: 3 eq., 6 unknowns

    Carlton writes on page 89: "The thrust of a marine propeller... may be expected to depend upon the following parameters: (a) The diameter (D) (b) the speed of advance (Va) (c) The rotational speed (n) (d) The density of the fluid (ρ) (e) The viscosity of the fluid (μ) (f) The static pressure of...
  26. J

    Trying to tie two runners of different speeds over a race

    Attempt is attached, thanks for the help :)
  27. T

    Block on top of moving slab, with a rough surface - When does v_b=v_s?

    For the first question I thought of using an energy balance, there is friction ##\Rightarrow \Delta E_m = -W_f##. Both at the start and at the end, the block has no velocity. Therefore ##E_{\text{initial}}= \frac 1 2 m_s v_{s,i}^2## and ##E_{\text{final}}= \frac 1 2 m_s v_{s,f}^2##. This means...
  28. I

    B How to determine applied force when two objects collide? (basic physics engine)

    I'm trying to make a very basic physics engine. So far I've got a variety of small things worked out but I've been driving myself crazy trying to work out collisions. From one sense I get I can use momentum and impulse to determine the velocity of an object after a fully elastic collision (no...
  29. M

    Two masses connected by Pulley - Lagrangian problem

    For this problem, My solution to (a) is, We have constraint ##x + y = L##. There are many places we could define our (x,y) Cartesian coordinate system. However, the most easiest I think for the problem would be to attach a ##x^*## and ##y^*## coordinate system at the COM of ##m_1##. We define...
  30. P

    Range of an object launched on a downward hill

    I managed to solve this by tilting the axes along the hill, and calculating the range, and then differentiating wrt ##\theta## (angle launched from hill) to get the answer. However, I recently came across the alternative solution below: The parabola it refers to represents the parabolic...
  31. P

    X and Y coordinates of an oscillating object on a spring.

    I get that: ##x(t) = A\cos(\omega t + \phi)## ##y(t) = A\sin(\omega t + \phi)## (from the above relevant equations). This agrees with the solution for part (a). However, the solution manual claims in part (b) that: In the case where ϕ1 = ϕ2 = 0 and A = B, the mass moves in a circle centered...
  32. P

    Kinematics: Acceleration of a figure skater changing direction

    My guess was simply that as acceleration changes from the north to east direction, the total magnitude change of v is ##v \sqrt 2##. Acceleration is ##\mu g##, so time would be ##\frac {v \sqrt 2} {\mu g}##. This agrees with the textbook solution. What I do not understand is the trajectory...
  33. Owen Ploe

    Need help, to help, a friend with their HW (High School)

    This is the problem set. I am stuck from this point... If anyone could give me a hand I would really appreciate it. I know this is probably really simple, but I don't know any of this and have been trying my best with youtube, and other peoples posts. PS this is for high school
  34. Jim Alexandridis

    Kinematics problem from a competition: Will the 2 sliding boxes collide?

    The distance covered by the first box is :s1max=v²/2|a|=v²/2μg where a=-μg by second newtons law Similarly S2max=(2v)²/2|a|=4v²/2μg It gas to be s1max+s2max≥S => v²/2a +4v²/2a ≥s => 5v²≥2aS =>v²≥ 2μgS/5=> v≥√(2μgs/5) But this is in the possible solution, am I wrong somewhere? I appreciate your help
  35. Gargi

    Query related to Two-Dimensional Motion

    My initial approach to this question was breaking the components of acceleration in the x and y axes and applying the three equations of motion to find the final velocity as well as the final position. As we were expected to find the net final velocity of the particle, I found the resultant of...
  36. D

    I Frame Transformation in rigid bodies

    I'm using rigid body dynamics/kinematics in robotics stuff but I don't have a background in mechanics, I'm interested in understanding the kinematics of frame transformations for rigid bodies. Suppose we have two reference frames fixed on a rigid body, F_1 and F_2 and a transformation T which...
  37. KukyZ

    How Much Vertical Acceleration Does a Jet Need to Avoid a Hill?

    The answer should be 10 m/s^2 but I don't know how to solve it
  38. P

    2 Masses and a Wheel (with mass)

    The equation that connects final velocity with distance traveled is ##v_f^2 = v_i^2 + 2a \Delta y## Since the system starts from rest ##v_i = 0## and the above equation becomes. ##v_f^2 = 2a \Delta y## Since there is rotation in this system we need to connect ##a## to the rotation of the...
  39. hello478

    Power, force, velocity and tension...

    my attempt: i solved it all correct but i dont understand a few things mentioned above... 82.04 * v = 56 so i got v as 0.68 m/s which is correct but i dont understand the concept...
  40. L

    Elliptical motion in polar coordinates

    I think I have completed the exercise but since I have seldom used polar coordinates I would be grateful if someone would check out my work and tell me if I have done everything correctly. Thanks. My solution follows. Since ##\left(\frac{x}{a}\right)^2+\left(\frac{y}{b}\right)^2=1## it follows...
  41. T

    Engineering How High Was the Balloon When the Stone Was Dropped?

    ay = -9.8. Vy = -9.8 + v0*Sin0. y = -4.9*t^2 + v0*t*Sin0. By using formula of y, my solution was -4.9(10s)^2 + (10m/s)(10s)Sin0. I assumed that y was equal to 0. Since -4.9 is m/s^2 the answer would be -490m + 100m*Sin0. Therefore I assumeed Sin0 = 490/100.
  42. W

    Prove this equation for projectile motion

    I tried using the formulas x=xi+vit and y=yi+voyt-1/2g(t^2) I assumed voy would be 0 and I almost arrive to the answer but idk how to get rid of the negative
  43. J

    Deriving a mathematical model for a stick falling over

    this is how far i have come with my model, i am trying to first the most simple model, meaning no friction involved and then testing that against an actual stick falling by using tracking software. I am currently stuck as my model still has an acceleration in the y direction that i cannot seem...
  44. R

    A ball is thrown w/initial speed vi at an angle 𝜃i with the horizontal

    A ball is thrown with an initial speed vi at an angle 𝜃i with the horizontal. The horizontal range of the ball is R, and the ball reaches a maximum height R/8. In terms of R and g, find the following. (a) the time interval during which the ball is in motion: Sroot(R/g) Correct (b) the ball's...
  45. Ineedhelpwithphysics

    'Police Car Catching Up' problem in kinematics

    Why is it 10.92 seconds and not 10 Cars displacement = 30*t +1/2(0)t^2 police displacement = 0*t + 1/2(6)(t)^2 30t = 3t^2 t = 10 seconds ???
  46. dom_quixote

    B What Are the Relativistic Implications for Beacon Synchronization?

    I propose to you a kinematics problem described by classical physics. Three space beacons A, B and C are 300,000,000 m (approximately one light second) apart. Beacon A emits a bright flash every three seconds. Beacons B and C respond instantly to the flash of Beacon A by emitting...
  47. ritzcrackers

    Maximize Your Swinging Ball Force with These Expert Tips

    idk
  48. D

    Projectile motion, initial height and range given, find initial velocity

    the answer to this question uses the above formula with the tangent function and solves for the initial velocity, i used the equation (v.sinθ^2) = (v.sinθ)^2 - 2gΔy, setting final velocity equal to zero and solving for initial velocity. this kinematic equation gives a different answer. can...
  49. brotherbobby

    B Kinematic equations ##\textbf{purely}## from graphs

    [FONT=times new roman]1. [FONT=times new roman]The first equation between velocity ##v## and time ##t## can be derived using the graph I have drawn for the purpose as shown on the right. Since acceleration ##a_0## is a constant, the graph of ##v-t## is a straight line. The slope of the line is...
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