# Homework Help: Simple Harmonics and also some pressure

1. Oct 4, 2012

### 2Big2Bite

1. The problem statement, all variables and given/known data
Hi

I have two problems i need to solve mainly 1, but i need to check if 2a and 2b is correct
here it is:

1. A simple harmonics oscillator has an amplitude of 0,1m.At what displacement will its kinetic and potential energies be equal

2. a) What is the force due to the atmosphere on one side of door of area 2m2?
b) If the difference in pressure on the two sides of a closed door of area 2m2 is 0,01 atm, what is the net force on the door? Do you think you could open it by hand?

2. Relevant equations
in first problem i though of using x=A/√2 where A is the amplitude but i have no idea how to solve this in any way other.

In the two other problems i though of using p=F/A and then in last problem find the difference with F1-F2

3. The attempt at a solution

1) Though trying putting the x=A/√2 = 0,07 but im not sure this is correct really since i just tried googling around for the answer and looking in the book.
Since our teacher give us this hint: v = dx/dt for x = Acoswt but idk how to use this.

2a) First i found F=P*A = 101300 Pa * 22 = 405200N

b) First i found the force F=P*A = 101300 Pa*0,99*2m2 = 401148 N

where the difference is F1-F2 = 405300-401148 = 4052N wich would make it quite hard to try open the door

2. Oct 4, 2012

### voko

If you know the velocity, what the kinetic energy? If you know the kinetic energy of an oscillator, what is its potential energy. Hint: KE + PE = const.