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 <----------
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
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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
To find the average velocity of a dropped brick that falls 4.0 m, you can use the formula v = d/t, where v is the average velocity, d is the distance the brick falls, and t is the time it takes to fall.
Given that the brick falls a distance of 4.0 m, we need to find the time it takes to fall. We can use the equation of motion: vf = vi + at, where vf is the final velocity, vi is the initial velocity, a is the acceleration, and t is the time.
In this case, vi is the initial velocity, which is given as 0 m/s (since the brick is dropped from rest), vf is the final velocity, which is also given as 0 m/s (since the brick comes to rest at the end of its fall), and the acceleration due to gravity, a, is given as 9.81 m/s^2.
Rearranging the equation vf = vi + at to solve for t, we have t = (vf - vi) / a. Substituting the given values, we get t = (0 m/s - 0 m/s) / 9.81 m/s^2. This simplifies to t = 0 / 9.81 = 0 s.
Since the time turns out to be 0 s, we need to use a different approach to find the average velocity. We can use the instantaneous velocity at any point during the fall instead. The instantaneous velocity at any point during a free fall can be calculated using v = gt, where g is the acceleration due to gravity, which is 9.81 m/s^2.
In this case, to find the average velocity, we can find the instantaneous velocity at the halfway point of the fall. Since the brick falls 4.0 m, the halfway point is at 2.0 m. Using v = gt, we get v = (9.81 m/s^2)(0.41 s) = 4.01 m/s.
Therefore, the average velocity of the dropped brick is approximately 4.01 m/s downward.