# Homework Help: Forced oscillations

1. Jan 11, 2005

### nemzy

A 2.00 kg mass attached to a spring is driven by an external force F = (2.00 N) cos (3t). Assume that the force constant of the spring is 25.0 N/m.

(a) Determine the period of the motion

(b) Determine the amplitude of the motion

FOr part A, i tried the T=2(pi)/w formula, and i got the wrong answer...what am i doing wrong?

For part B, the book says to use this formula:

A= Fo/m / square root of [ (w^2-wo^2)+(bw/m)^2 ]

the Bw/m^2 is irrelevent since B=0....

But what is Fo? Is this how u are suppose to solve for the amplitute for this problem? thanks

2. Jan 11, 2005

### remcook

first write down the equation of motion before plugging in some formulas. all these oscillation questions you have, have the same kind of equations of motion. first write them down and then solve these equations. don't rely on rules of thumb.

3. Jan 11, 2005

### HallsofIvy

What course is this? These look like problems from a differential equations course, but you haven't said anything about solving any differential equations.

PLEASE tell us what your notation means in this particular problem. There is no way we can say what B or Fo mean. Those have to be defined when the formulas are given.

4. Jan 11, 2005

### nemzy

B=constant related to the strength of the resistance force

and Fo is

F(t)=Fo(sin(wt))