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zzz [600]
3 years ago
7

an elevator mass of 7700 kg falls from a height of 32 m after a sudden failure in the hoisting cable. The mass is stopped by a s

pring at the bottom of the shaft. Determine the spring constant (in kN/m) necessary to bring the elevator and occupants to rest without exceeding an acceleration of 5 g's.
Physics
1 answer:
valkas [14]3 years ago
4 0

Answer:k=28.29 kN/m

Explanation:

Given

mass m =7700 kg

height from which Elevator falls h=32 m

Let x be the compression in the spring

thus From conservation of Energy Potential energy will convert in to Elastic Potential Energy of spring

\frac{kx^2}{2}=mg(h+x)----------1

also maximum acceleration is 5g

thus

mg-kx=ma

here a=-5g

kx=mg-m(-5g)=6mg

x=\frac{6mg}{k}

Substitute x in equation 1

0.5\times k\times (\frac{6mg}{k})^2=mg(h+\frac{6mg}{k})

18\frac{(mg)^2}{k}=mgh+6\frac{(mg)^2}{k}

k=12\cdot \frac{mg}{h}

k=12\times \frac{7700\times 9.8}{32}

k=28.29 kN/m

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