Physics (Kinematics Check)

What is the average velocity of a dropped brick that falls 4.0 m?

vi = 4.0 m/s
vf = 0 m/s
a = 9.81 m/s^2

t = vf-vi / a
t = -4/9.81
t = 0.41 s

v = d/t
v = 4.0/0.41
v = 9.81 m/s^2 <----------

  1. 👍 0
  2. 👎 0
  3. 👁 88
asked by Lucina
  1. actually I think vi, your initial speed is zero
    we do not know vf, the final speed. All we know is that it fell 4 m.

    h = Hi + vi t - (1/2) g t^2
    0 = 4 + 0 - (1/2)(9.81) t^2
    so
    t^2 = 4/4.9
    t = .9035 seconds to fall 4 meters

    the average speed is 4 meters/.9035seconds
    or 4.43 m/s

    ========================
    by the way you can find vf, the final speed when it hits the ground
    vf = 9.81 t = 9.81(.9035) = 8.86 m/s
    the average is then (0 +8.86)/2
    which is sure enough 4.43 m/s

    1. 👍 0
    2. 👎 0
    posted by Damon

Respond to this Question

First Name

Your Response

Similar Questions

  1. Physics

    A 9 kg lead brick falls from a height of 1.8 m. a) Find the momentum as it reaches the ground. b) What impulse is needed to bring the brick to rest? c) The brick falls onto a carpet 2.0 cm thick. Assuming the force stopping it is

    asked by Jayd on November 7, 2007
  2. calculus

    A brick becomes dislodged from the top of a state building (at a height of 1290 feet) and falls to the sidewalk below. (a) Write the position, velocity, and acceleration functions of the brick. s(t) = v(t) = a(t) = (b) How long

    asked by Brandi on March 6, 2013
  3. Math3(Reiny Please Help)

    An object on Earth falls with an acceleration of a=9.81 m/s^2. A function exists between the height from which the object falls, the initial velocity of the object and the time the object spends in the air. h(t)= Vt + at^2

    asked by Heaven on May 17, 2016
  4. Engineering science

    A brick with a mass of 6kg is dropped vertically from a certain height.it takes 4,5 seconds for the brick to reach the ground.determine the ff.the height from which the brick is dropped and potential energy of the brick

    asked by Peter on March 8, 2014
  5. physics

    A brick is dropped (zero initial speed) from the roof of a building. The brick strikes the ground in 3.05 s. You may ignore air resistance, so the brick is in free fall. (a) How tall, in meters, is the building? (b) What is the

    asked by kylie on December 15, 2016
  6. Finding Velocity

    A brick falls freely from a high scaffold. A. What is its velocity after 4.0s? B. How far does the brick fall during the first 4.0s? I don't know what formula to use. I only have time, and I guess the first velocity would be 0s.

    asked by -Untamed- on October 9, 2011
  7. physics

    a brick is dropped (0 initial speed) from the top of a building. the brick strikes the ground in 2.5 seconds. you may ignore air resistant so the brick is in free fall. A)how tall in meters is the building? B) what is the

    asked by josh on July 18, 2010
  8. physics

    a construction worker accidentally knocks a brick from a building so that it falls in 4s to the ground.calculate a) the velocity of the brick as it hits the ground b)the distance fallen of the brick

    asked by shiva on March 23, 2012
  9. SCIENCE

    A BRICK WITH MASS OF 6 KG IS DROPPED VERTICALLY FROM A CERTAIN HEIGHT. IT TAKES 4.5 SECONDED FOR THE BRICK TO REACH THE GROUND DETERMINE THE FF. THE HEIGHT FROM WHICH THE BRICK IS DROPPED THE SPEED OF WHICH THE BRICK THE GROUND IT

    asked by BRONWYNNE on June 13, 2016
  10. Physics

    A brick is dropped from a high scaffold. (a) What is its velocity after 4.5 s? m/s (b) How far does the brick fall during this time?

    asked by Billy on January 14, 2013

More Similar Questions