Position of an object in time and force

[preluderacer]

Homework Statement

The position of an object as a function of time is given by = bt^3 ihat + ct jhat . If and , what is the force on a 2.0 kg object when t = 1.8 s?

The Attempt at a Solution

I tried multiplying it and got m ihat + m jhat. I don't even know where to begin.

 

[rl.bhat]

If and , what is the force on a 2.0 kg object when t = 1.8 s?

This statement is not clear. Rewrite it.

 

[preluderacer]

The position of an object as a function of time is given by = bt^3 ihat + ct jhat . If b=2.1m/s^3 and c=1.7m/s, what is the force on a 2.0kg object when t=1.8s

 

[rl.bhat]

Let x = bt^3 ihat + ct jhat
Find a = d^2(x)/dt^2 and substitute t = 1.8 s
Now find F.

 

[preluderacer]

so x=(bt^3ihat +ct)?

then u want me to find the derivative?

 

[preluderacer]

Ha, I went to get breakfast and kept thinking about it. It goes position, velocity, then acceleration. So I take the 2nd derivative with respect to time, then use f=ma. Thanks you! =)