# can anyone explain how to do this

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NURUL ATIKAH AZALI on 11 Jul 2021
Commented: Ahmed Moh'd Salem on 12 Jul 2021
A spring is stretched by 175 mm an 8 kg block. If the block is displaced 100 mm downward from its equilibrium position and given a downward velocity of 1.50 m/s, determine the differential equation which describes the motion. Assume that positive displacement is downward. Determine the position of the block when the weight decreased from 8 kg until 4 kg?
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Ahmed Moh'd Salem on 12 Jul 2021
The quastion should be solved by using Matlab

Jonas on 11 Jul 2021
so if you put 8kg on the spring it moves 175mm down and does not move further. this means there is a force equlibrium between the weight and the spring which you can use to calculate the spring constant k
k*0.175m=8kg*9.81m/(s^2)
from that you can also solve the 4kg question
the motion will follow a cosine function A*cos(2*pi*f*t). the frequency is sqrt(k/m)/(2*pi), the amplitude is given and the starting speed gives you the condition for the dervative of the motion