Tbr ps cbt 6

[greenseeking]

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If a seismic recorder whose design is built around a vertical hanging spring is too sensitive, what adjustments can be made to the instrument to correct its reading?

A. Increase the spring constant, and mount the sensor on more solid ground.
B. Increase the spring constant, and mount the sensor on less solid ground.
C. Decrease the spring constant, and mount the sensor on more solid ground.
D. Decrease the spring constant, and mount the sensor on less solid ground.

Answer is B.
I can eliminate C and D becuase spring constant should be increased. But why should the sensor be on less solid ground? wouldn't the ground shake the recorder more and make it even more sensitive? I chose A.

 

[Jepstein30]

If a seismic recorder whose design is built around a vertical hanging spring is too sensitive, what adjustments can be made to the instrument to correct its reading?

A. Increase the spring constant, and mount the sensor on more solid ground.
B. Increase the spring constant, and mount the sensor on less solid ground.
C. Decrease the spring constant, and mount the sensor on more solid ground.
D. Decrease the spring constant, and mount the sensor on less solid ground.

Answer is B.
I can eliminate C and D becuase spring constant should be increased. But why should the sensor be on less solid ground? wouldn't the ground shake the recorder more and make it even more sensitive? I chose A.

Hmmm same here, I'd go A.. definitely not C/D because you'd want a more stiff spring..

anything in the passage?

 

[greenseeking]

Hmmm same here, I'd go A.. definitely not C/D because you'd want a more stiff spring..

anything in the passage?

no passsage it's a free standing question.

answer key said something about how a less solid ground would be able to absorb some of the displacement from the seismic wave? I mean I guess it KINDA makes sense but it kinda doesn't.

 

[LoLCareerGoals]

Put a solid rock and move it right by some distance.
Now do the same to a bunch of small pebbles.
Center of which of the 2 masses experienced the most displacement? (assuming the instrument is at the center).

Also why would post the answer right away? Give people a chance to practice. Such a great/imagination demanding problem.

 

[farnell]

Think about it this way- if the ground is solid, all of the force on the spring will push down on it and the change I length Of the spring will be great. If the ground is compressible, some of the energy will be transferred from the spring to the ground, and the spring will condense less. You would need more force to compress the spring the same distance as on hard ground, so it is less sensitive to change on soft ground.

Imagine the force needed to compress a string on a trampoline vs on concrete. You need more force to compress the spring the same distance on the trampoline.

 

[greenseeking]

Think about it this way- if the ground is solid, all of the force on the spring will push down on it and the change I length Of the spring will be great. If the ground is compressible, some of the energy will be transferred from the spring to the ground, and the spring will condense less. You would need more force to compress the spring the same distance as on hard ground, so it is less sensitive to change on soft ground.

Imagine the force needed to compress a string on a trampoline vs on concrete. You need more force to compress the spring the same distance on the trampoline.

Hm. your explanation is most helpful. So what I am visualizing is that the sensor is mounted on the ground (firm or shaky) and in the sensor is a vertical spring. Is the vertical spring attached on both ends or is it attached on one end and free on the other?