rgtsjzfg
Badges: 0
Rep:
?
#1
Report Thread starter 6 years ago
#1
A simple pendulum of time period 1.90 s is set up alongside another pendulum of timeperiod 2.00 s. The pendulums are displaced in the same direction and released at thesame time. Calculate the time interval until they next move in phase. Explain how you arrive atyour answer. (3 marks)

I don't understand the mark-scheme of the question. Can somebody explain how to answer this question?
0
reply
randlemcmurphy
Badges: 11
Rep:
?
#2
Report 6 years ago
#2
(Original post by rgtsjzfg)
A simple pendulum of time period 1.90 s is set up alongside another pendulum of timeperiod 2.00 s. The pendulums are displaced in the same direction and released at thesame time. Calculate the time interval until they next move in phase. Explain how you arrive atyour answer. (3 marks)

I don't understand the mark-scheme of the question. Can somebody explain how to answer this question?
Assume the pendulum with T=1.90s, does one oscillations, hence T=1.90s. Now how many oscillations will the other pendulum with T=2.00s have to do to have the same T=1.90s as the first pendulum?

So:

1(1.9)=y(2.00) (Where y is the number of oscillations)

It should be fairly obvious that y=1.90/2.00 oscillations.

So:

1(1.90)=(1.90/2.00)(2.00)

However we need when they will be in phase after a whole number of oscillations, we can do this via multiplying by 2.00

So: 2.00(1.90)=(1.90)(2.00)

We need to x10 to get a whole number of oscillations.

So they will next be in phase when the pendulum with T=1.90 does 20 oscillations and the pendulum with T=2.00s does 19 oscillations, it should be obvious how to calculate this time now. It is the LCM so the first time they become in phase.

SIDE-NOTE:

You could have used the idea that the pendulum with T=2.00s would have to do one less oscillation than the pendulum with T=1.90s
Hence you could have set up the equation:

(n)1.90=(n-1)2.00 (Where n is number of oscillations)

Solve for n and thus the time.
7
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

How do you prefer to get careers advice?

I like to speak to my friends and family (8)
10.96%
I like to do my own research online using careers specific websites (50)
68.49%
I like speaking to the careers advisors at school, college or uni (10)
13.7%
I prefer to listen watch videos or listen to podcasts of people in my chosen career (4)
5.48%
Something else (let us know in the thread) (1)
1.37%

Watched Threads

View All
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise