SHM (1 Viewer)

[wandering17]

http://www.yiminmathcentre.com/homework/year12/Year12_Topic_9_Motion_Part2.pdf

I dont understand the example on page 9/15

"a weight hanging from the roof on an elastic string is moving in SHM. It takes 4 secs to move from the bottom of its motion, 15 cm above the floor......"

Can someone please explain how they got 35 cm? And how theyre just choosing stuff please

The example was taken from cambridge book

 

[rand_althor]

The bottom of the motion is 15cm from the ground, and the top is 55cm from the ground. The weight is travelling 40cm from top to bottom. At halfway, it will have travelled 20cm. 15+20=35cm from the ground.

 

[Silly Sausage]

Consider the amplitude at the origin. The minimum amplitude is 15cm above the floor whilst the maximum amplitude is 55cm above the floor. The origin is between the minimum and maximum amplitude. Therefore it is exactly between 15cm and 55cm. (15cm+55cm)/2 =35cm.