physics

posted by .

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 ?

  • physics -

    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

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Physics/Science #2

    A rock is thrown verticaly upward from ground level at time t = 0. At t = 1.65 s it passes the top of a tall tower, and 0.95 s later it reaches its maximum height. What is the height of the tower?
  2. physics

    a stone is thrown vertically upward with an initial velocity u from the top of tower, reaches the ground with a velocity 3u. what is the height of tower?
  3. Math

    The height(h) of an object that has been dropped or thrown in the air is given by: h(t)=-4.9t^2+vt+h t=time in seconds(s) v=initial velocity in meters per second (m/s) h=initial height in meters(m) A ball is thrown vertically upwardd …
  4. science

    A tower is 24m high. A stone is projected upwards from the tower with initial velocity of 24,5 m/s. Calculate how long it would take for the stone to reach the ground at the foot of the tower.
  5. Physics

    A stone is thrown vertically upward from the top of the tower with a velocity of 15m / s. Two seconds later a second stone is dropped from the top of the tower.if both the stone strike the ground simultaneously find the height of the …
  6. Physics

    An airplane flies clockwise around an airport control tower at a speed of 190 m/s. If that control tower is 8 km from the airplane at all times, what is the plane’s angular velocity (magnitude and direction)?
  7. calculus

    Baseball Star Bryan is standing at the top of the Sears Tower in Chicago and decides to throw a baseball up with a velocity of 5 m/s. The Sears Tower is 442 meters tall and gravity exerts a constant acceleration of -9.8 m/s/s. Ignore …
  8. College Algebra

    A person who is 6 feet tall walks away from a 50-foot tower toward the tip of the tower's shadow. At a distance of 32 feet from the tower, the person's shadow begins to emerge beyond the tower's shadow. How much farter must the person …
  9. physics

    A ball reaches the ground at 6 seconds when thrown vertically upwards from the top of a tower with an inoitial velocity 24m/s. Find the height of the tower.
  10. science

    A ball is thrown upward from the top of a 35-m tower, with initial velocity of 80m/s at an angle of 25 (a) find the time to reach the ground and the distance from the base of the tower to the point of impact (b) find the magnitude …

More Similar Questions