The Tri-State Tornado of 1925 was the deadliest in U.S. history. It tracked thro

Question

The Tri-State Tornado of 1925 was the deadliest in U.S. history. It tracked through three Midwestern states, leaving 695 people dead. In the aftermath, a 15-cm-diameter barn pole was found embedded into the ground to a depth of 1.62 m. It is estimated that the pole was traveling at a speed of 94.6 m/s at the time. Calculate the magnitude of the pole's acceleration (assumed to be constant) as it was penetrating the ground. Enter your answer m/s2 Dental X-rays are created by accelerating electrons through a short distance, then the electrons travel at constant speed until they strike a metal target. Suppose that starting from rest, the electrons accelerate at 6.8 × 1013 m/s2 through a distance of 2.02 cm, then travel another 15 cm before striking the metal target. Calculate the time it takes an electron to travel the total distance.

Explanation / Answer

given, the pole was d = 1.62 meter deep in soil
so, initial speed of pole, v = 94.6 m/s
lets pole's acceleration be a
then 2*a*d = -v^2
2*a*1.62 = - 94.6^2
a = -2762.086 m/s/s
-ve sign indicates that tghe pole was decelerated

initial velocity of electrons u = 0
acceleration, a= 6.8*10^13 m/s/s
distance, d = 2.02 cm = 0.0202 m
final velocity , v = ?
2*a*d = v^2 - u^2
2*6.8*10^13*0.0202 = v^2
v = 1.657*10^6 m/s
time taken for this part, t1 = ?
v = u + at
t1 = 1.657*10^6/6.8*10^13 = 2.437*10^-8 s

then the electron travels s = 0.15 m
so time taken t2 = s/v = 0.15/1.657*10^6 = 9.05*10^-8 s

total time = t1 + t2 = 11.489*10^-8 s

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