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# Time period and Frequency

Hello Brilliantians,

There was an interschool science quiz held today which had the following question:

A pendulum oscillates at the RATE of 5 oscillations per minute on EARTH. What will happen to the TIMEPERIOD of the same pendulum when it is placed on the MOON? Will it increase or decrease? Give reason for your answer.

I answered that the time period will increase because the frequency will decrease on the Moon. According to me, due to the less gravitational pull on the moon(1/6th as that of earth), the pendulum will oscillate with a less speed (frequency), and hence the timeperiod will increase.

My team wasn't awarded any points for the answer. The quizmaster said that the time period will decrease, but he too gave the same reason that I had given.

Note by Ritu Roy
2 years, 7 months ago

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Frequency of a pendulum varies proportional to the square root of acceleration due to gravity(g) of that place. Timeperiod of pendulam varies inversely to the sq. root of' g'. Hence, the frequency of pendulam on the surface of moon becomes 2.04 oscillation/minute. But the time period of the pendulam at moon surface will be 2.449 times that at earth! So you were right before quiz master. · 2 years, 7 months ago

2 equal perpndicular forces, if the angle between resultant force and x axis is 45 degree and resultent force =20 n , find a] fx b] fy c] vector product d] scalar product please help me its my first time · 1 year, 8 months ago

@PRABIR CHAUDHURI Thankyou for the explanation sir · 2 years, 7 months ago

@tytan le nguyen , @Vaibhav Sharma , @Vibhav Agarwal , @PRABIR CHAUDHURI and @Ishan Mishra : Thanks for the responses. · 2 years, 7 months ago

interesting · 2 years, 7 months ago

to me also it looks like that time period will increase!! · 2 years, 7 months ago

@Vibhav Agarwal Oh! So, is the answer correct or the quizmaster wrong??? · 2 years, 7 months ago

i believe the quizmaster is wrong which is hard to believe!! · 2 years, 7 months ago

Thankyou for the reply · 2 years, 7 months ago

Strange, I understand your reasoning but I feel that T should increase:

If I remember correctly, Time period ≈ 2∏ √(l/g) π is constant, l is constant so the only thing that changes is g.

The Earth has a higher g value than the moon. Thus, for the moon, g is lower. Because T is inversely proportional to g, if g decreases then T should increase. · 2 years, 7 months ago

He did say that T would increase. The quizmaster said it would decrease, but it was for the exact same reason. Therefore, I believe the quizmaster is incorrect in this rare case. · 2 years, 7 months ago

actually your quiz master was wrong. T = 2∏√( L / g) T: Time L: Length of Pendulum g: Gravitational Force so clearly, if g is decreased time period will increase · 2 years, 7 months ago