# Force on Mass

1. Jan 29, 2013

### kopinator

The position of a mass m = 28.0 kg is given in by x(t) = 3.0sin ((15.0)t). Calculate the magnitude of the maximum force acting on the mass.

F=ma. I tried deriving x(t) twice to get the acceleration equation so i could plug it into F=ma and then pick a random number for t. I chose t=1 but i still didn't get the right answer.

2. Jan 29, 2013

### rock.freak667

Hint: the maximum value of sin(kt) or cos(kt) is 1 where k is any constant.

3. Jan 29, 2013

### kopinator

So I guessed correctly with t=1. But I'm still stumped on where to go from there. Do I still take the 2nd derivative of x(t)?

4. Jan 29, 2013

### SteamKing

Staff Emeritus
You are confusing the maximum value of sin(kt) with the value of t.

If k = 1, is sin (1) a a maximum? Sin (x) and Cos (x) both have maximum values of 1, but the x values where this occurs are different.