physics

A train passes a control tower with a velocity u and has a constant acceleration.At 800m beyond the tower,the velocity is 48km/h;and at 1.6km beyond the tower,the velocity is 64km/h,what is the velocity u ?

  1. 👍 0
  2. 👎 0
  3. 👁 128
  1. V2 = 48000/3600 = 13.33 m/s
    V3 = 64000/3600 = 17.78 m/s

    average speed between points 2 and 3 =(13.33+17.78)/2
    = 15.56 m/s

    distance between points 2 and 3 =1600 -800 = 800 m

    time between points 2 and 3 = 800/15.56 = 51.4 seconds

    acceleration = a = change in speed over time
    a = (17.78-13.33)/51.4 = .0866 m/s^2

    now between point 0 and point 1
    v = u + a t
    13.33 = u + .0866 t or u = (13.33-.0866t)
    x = 0 + ut +(1/2)at^2
    800 = u t +(1/2)(.0866) t^2
    so
    800 = (13.33-.0866t)t +.0433 t^2
    solve quadratic for t, go back and get u

    1. 👍 0
    2. 👎 0

Respond to this Question

First Name

Your Response

Similar Questions

  1. physics

    two ends of a train moving with constant acceleration pass a certain point with velocities u and v. what is the velocity with which the middle point of the train passes the same point? I have asked this question before you have

    asked by pavatharani on July 3, 2011
  2. Physics

    A 90 m long train begins uniform acceleration from rest. The front of the train has a speed of 21 m/s when it passes a railway worker who is standing 184 m from where the front of the train started. What will be the speed of the

    asked by Sydney on September 13, 2011
  3. F.maths

    XYZ are three points on a straight road.A car passes X with a velocity of 5m/s.It travels from X to Y with a constant acceleration of 2m/s^2 and from Y to Z with constant retardation of 3.5m/s^2.find the velocity of the car as it

    asked by Kosy on September 14, 2014
  4. Physics

    Liz rushes down onto a subway platform to find her train already departing. She stops and watches the cars go by. Each car is 8.60 m long. The first moves past her in 1.75 s and the second in 1.17 s. Find the constant acceleration

    asked by Erin on October 10, 2009
  1. Math

    From an aeroplane in the air and at a horizontal distance of 1050m, the angles of depression of the top and base of a control tower at an instance are 〖36〗degrees and 〖41〗degrees respectively. Calculate, correct to the

    asked by Sharon on May 8, 2020
  2. physics

    a train starts from rest and accelerates unifotmly, until it has travled 3.7 km and acquired a velocity of 30 m/s. the train then moves at a constant velocity of 30 m/s for 410 s. the train then slows down uniformly at 0.065

    asked by heaven on June 10, 2013
  3. physics

    a train 100m long is to cross a river bridge of length 800m. what time it take to cross the bridge ?velocity of train is 36km/h.

    asked by akanksha on June 7, 2014
  4. Physical Science

    So, please check my answers here: 1. Which example identifies a change in motion that produces acceleration? A) A speed skater moving at a constant speed on a straight track** B) A ball moving at constant speed around a circular

    asked by Rosie on January 18, 2020
  1. Science help! URGENT. Check answers

    1. True or False? A model train traveling at a constant speed around a circular track has a constant velocity. (False) 2.Which of the following would be affected if a soaring eagle changed direction but remained at a constant

    asked by Elena on October 15, 2013
  2. Physics (12)

    A car and train move together along parallel paths at 25 m/s [W]. The car then undergoes a uniform acceleration of 2.5m/s^2 [E] because of a red light and comes to rest. It remains at rest for 45s, then accelerates back to a

    asked by Brooke on September 11, 2007
  3. physics

    a train starts from rest and accelerates unifotmly, until it has travled 3.7 km and acquired a velocity of 30 m/s. the train then moves at a constant velocity of 30 m/s for 410 s. the train then slows down uniformly at 0.065

    asked by Anonymous on June 10, 2013
  4. physics

    A man named Harold is standing in a train car that has no windows. Since there aren't any windows, he doesn't know how fast or in what direction the train is moving or whether it is accelerating or decelerating. Harold decides

    asked by Michelle on February 11, 2015

You can view more similar questions or ask a new question.