A projectile is shot straight upward from the earth with a speed of 20 m/s. How high is it when its speed is 8.0 m/s? Ignore air friction. (Hint: The projectile's energy is conserved)

Question

Physics

Emmalee Barrett

8 April, 16:15

A projectile is shot straight upward from the earth with a speed of 20 m/s. How high is it when its speed is 8.0 m/s? Ignore air friction. (Hint: The projectile's energy is conserved)

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Answers (1)

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Abbey Burgess · Answer 1

The first thing you should do for this case is to write the kinematic equations of the object in the vertical direction.

For this case, we have

a = - 9.8 m / s ^ 2

Vf = a * t + Vo

clearing time:

t = (Vf-Vo) / (a)

t = ((8) - (20)) / (( - 9.8)) = 1.22 s

the position of the object for that time and for when V = 8.0 m / s is

y (t) = a * t ^ 2/2 + Vot + I

y (1.22) = ( - 9.8) * (1.22) ^ 2/2 + (20) (1.22) + 0 = 17.11m

answer

the projectile is 17.11m high when its speed is 8.0 m / s