Help Please, ty A ball is launched at 20 meters per second (m/s) from a 60 meter tall platform. The equation for the object's height s at time t seconds after launch is s(t) = –4.9t2 + 20t + 60, where s is in meters.  What is the height above the ground when the object is launched? How long before the object hits the ground after launch? What is the maximum height of the object?

  1. 👍
  2. 👎
  3. 👁
  1. s = height above ground
    s = 60 + 20 t - 4.9 t^2 (standard physics equation on earth)

    at t = 0
    s = 60 (clearly :)

    now when does it hit the bleak earth?
    That is when s = 0
    4.9 t^2 - 20 t -60 = 0
    solve quadratic and use the positive t (the negative t was back before you threw it if you had thrown it from the ground)
    t = 6.09 or - 2.01
    use t = 6.09

    now to do the last part there are two obvious ways to get t at the peak
    1. look for vertex of parabola
    2. look for halfway between t = -2.01 and t = 6.09
    I will do it the hard (11) waay by completing the square
    4.9 t^2 - 20 t = -(s-60)
    t^2 - 4.08 t = -.204 s + 12.2
    t^2 - 4.08 t +2.04^2 = -.204 s +12.2 + 4.16

    (t-2.04)^2 = -.204(s-80.2)
    top at 80.2 meters at t = 2.04 s
    quick check on time
    should be average of 6.09 and -2.01
    =4.08 /2 = 2.04 check

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. Physics

    2. Consider the ball example in the introduction when a ball is dropped from 3 meters. After the ball bounces, it raises to a height of 2 meters. The mass of the ball is 0.5 kg a. What is the speed of the ball right before the

  2. Algebra

    A ball is thrown from an initial height of 2 meters with an initial upward velocity of 25m/s. The ball's height h (in meters) after t seconds is given by the following. Find all values of t for which the ball's height is 12

  3. Calc

    A baseball is thrown upwards from a height of 2 meters with an initial velocity of 10 meters per second. Use the fact that -9.8 meters per second squared is constant acceleration due to gravity to answer the following: The maximum

  4. Differential Equations

    A projectile was launched from the ground with a certain initial velocity. Militaries used a radar to determine the vertical coordinate y(t) of the projectile for two moments of time t measured in seconds from the moment when the

  1. grade 11 physics

    A championship golfer uses a nine iron to chip a shot right into the cup. If the golf ball is launched at a velocity of 20 m/s at an angle of 45° above the horizontal, how far away was the golfer from the hole when he hit the

  2. physics

    A ball is released from a tower at a height of 100 meters toward the roof of another tower that is 25 meters high. The horizontal distance between the two towers is 20 meters. With what horizontal velocity should the ball be

  3. physics

    A ball is released from a hot air balloon moving downward with a velocity of -10.0 meters/second and a height of 1,000 meters. How long did it take the ball to reach the surface of Earth? Given: g = -9.8 meters/second2.

  4. physic

    A cannon ball is fired at an angle of 30° above horizontal with an initial speed vi = 55 m/s. Assume the cannon ball leaves the cannon at ground level and ignore air resistance. (a) How long is the cannon ball in the air? (b) How

  1. algebra 1 connexus

    A baseball player throws a baseball directly upward into the air. The height of the ball is given by the equation y=−4.9x^2+89.5x+1.75 where y is the height in meters and x is the time in seconds. Is this equation a reasonable


    An object is launched from the ground into the air at an angle of 38.0 o (above the horizon) towards a vertical brick wall that is 15.0 m horizontally from the launch point. If the ball takes 1.30 seconds to collide with the wall,

  3. algebra

    A ball is thrown upward with an initial velocity of 14 meters per second from a cliff that is high. The height of the ball is given by the quadratic equation H = 49t^2 + 14t +60 where h is in meters and t is the time in seconds

  4. Physics

    On a distant planet, golf is just as popular as it is on earth. A golfer tees off and drives the ball 4.1 times as far as he would have on earth, given the same initial velocities on both planets. The ball is launched at a speed

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