1. The problem statement, all variables and given/known data An object with mass m moves along the x axis. It's position as a function of time is given by X(t)= At- Bt^2 + Ct^3 A,B,C are constants a) find expression for the net force acting on the object as a function of time. b) let A= 2m/s, B= 10m/s^2, and C= 1m/s^3 c) at what position is the net force 0? d) Sketch graphs of the velocity and force vs time... 2. Relevant equations F=ma The equation given 3. The attempt at a solution a) eqzn for the net force acting on the object as a function of time... I have not a clue...is it I find the acceleration equation and then go and say m= constant so it doesn't matter? x(t)=Ct^3 -Bt^2 + At v(t)= x'(t)= 3Ct^2-2Bt +A a(t)= v'(t)= 6Ct- 2B ==> is this it but how do I add m?? I assume since m is a constant so only thing changing is a, Am I correct? b) when net force = 0 plugged in the numbers x(t)= t^3 - 10t^2 + 2t a(t)= 6Ct- 2B a(t) 6t- 20 when is the force 0?? isn't it when accleration= 0?? and time is.. 0= 6t-20 20/6= t t= 3.33s c) value of velocity when net force = 0 v(t)= x'(t)= 3Ct^2-2Bt +A v(t)= 3t^2 - 20t + 2 t= 3.33 when net force = 0 plugging in.. v(3.33)= 3(3.33)^2- 20(3.33) + 2 v= -31 m/s Is this alright???