Find the acceleration due to gravity

[zade70]

Homework Statement

A person shakes pendulum with length 3.6 meters. For 12 shakes he measured the time of 38 seconds. Find the acceleration due to gravity

Homework Equations

T=t/n
T=2*pi*sqrt(l/g)

The Attempt at a Solution

T(period)=t/n=3.167
T=2*pi*sqrt(l/g) l-length
g=4*(pi)^2*l/T^2
g=14.156
The solution in my book is 9.4 m/s^2. Where is my error?

 

[gneill]

Your solution method looks fine.

Perhaps there's an error in the book (Sometimes they update problems with new editions but fail to update the answer key), or there's something about the definition of "shakes" that we're missing. Is the problem statement a translation?

 

[zade70]

Your solution method looks fine.

Perhaps there's an error in the book (Sometimes they update problems with new editions but fail to update the answer key), or there's something about the definition of "shakes" that we're missing. Is the problem statement a translation?

Yes

 

[gneill]

What is the original language? Is there more information in the original problem statement that you haven't shown?

 

[zade70]

What is the original language? Is there more information in the original problem statement that you haven't shown?

I have given all the information. The correct answer is 9.4 m/S^2

 

[gneill]

Your answer is correct (if you round to the correct number of significant figures). I don't agree with the book's answer.

 

[gneill]

Was the pendulum a simple pendulum (mass bob on a string) or something else, like a solid rod?

 

[zade70]

When we do similar problems we consider the pendulum like this http://dev.physicslab.org/img/14c7c356-6f6e-49e4-a953-2396343435fb.gif. The problem just says a pendulum is vibrated.

 

[gneill]

When we do similar problems we consider the pendulum like this http://dev.physicslab.org/img/14c7c356-6f6e-49e4-a953-2396343435fb.gif. The problem just says a pendulum is vibrated.

Okay, so simple pendulum it is:

Then again, I support your result and not the book's.

 

[The Vinh]

Saloni Khanna, post: 5419032, member: 588906"]

Okay, so simple pendulum it is:
View attachment 97843

Then again, I support your result and not the book's.

gneill, did you use paint to draw that picture or what program did you use, i really want to know . Sorry for saying something not related to OP

 

[gneill]

gneill, did you use paint to draw that picture or what program did you use, i really want to know . Sorry for saying something not related to OP

The picture came from the OP's link. I just cut-and-pasted it to make it visible in-thread; off-site links have a tendency to disappear over time.

I do make quite a few images for posting here though. I use an old version of Visio to make them.

 

[The Vinh]

The picture came from the OP's link. I just cut-and-pasted it to make it visible in-thread; off-site links have a tendency to disappear over time.

I do make quite a few images for posting here though. I use an old version of Visio to make them.

many thanks to you