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Physics simple harmonic motion

2. Geoff, a rock climber, is following his friend Marie up an overhanging cliff. Marie is attached to the rock
and ensures that the rope between herself and Geoff is taut at all times. Unfortunately, Geoff falls off
and subsequently swings. Unless otherwise stated, ignore air resistance.
Total for Question 2: 24
(a) Geoff passes through the equilibrium position, for the second time, after 4.5 s. At this point, he is
travelling at a speed of 5 ms−1
. Calculate the following:
i. The frequency of his oscillations. [2]
ii. His velocity 2.25 s after he falls.
Answer to ii part is - 3.54 but how to get it?
Reply 1
Which part are you stuck with? The vertical amplitude about the equilibrium will be described by the usual
A cos(wt)
Have you got the frequency in i) and amplitude?
(edited 2 years ago)
Reply 2
Original post by mqb2766
Which part are you stuck with? The vertical amplitude about the equilibrium will be described by the usual
A cos(wt)
Have you got the frequency in i) and amplitude?

yes I got those 2, frequency and amplitude but I am struggling with velocity after 2.25 sec.
Reply 3
Original post by Atht123
yes I got those 2, frequency and amplitude but I am struggling with velocity after 2.25 sec.

What did you get for the frequency and amplitude?
If you have those, just differentiate to get the velocity and sub in the time.
(edited 2 years ago)
Reply 4
Original post by mqb2766
What did you get for the frequency and amplitude?
If you have those, just differentiate to get the velocity and sub in the time.

For frequency I got 0.17 sec-1 and for Amplitude I got 4.67 m, but still how do I get velocity which formula I will use, can you plz do it and show me 😢
Reply 5
Original post by Atht123
For frequency I got 0.17 sec-1 and for Amplitude I got 4.67 m, but still how do I get velocity which formula I will use, can you plz do it and show me 😢

x = A cos(wt) = A cos(2*pi*f*t)
So differentiate with respect to time to get the velocity v = dx/dt = ...
(edited 2 years ago)
Reply 6
Original post by mqb2766
x = A cos(wt) = A cos(2*pi*f*t)
So differentiate with respect to time to get the velocity v = dx/dt = ...

ok thanks a lot , i think i got it :smile:

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