# Help displacement problem

1. Jun 30, 2011

### Jimmy84

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

Determine the displacement of this particle from t=1s to t=3s

r=-(5,0m/s)t i + (10,0m/s^2)t^2 j + (7,0m -(2,0m/s^3)t^3) k

2. Relevant equations

3. The attempt at a solution
I dont have an idea how to do this if I should to it by replacing t by 1 and then getting the magnitude of the vector for example. or should i get the value of t = 1 by each component alone and substract the components of 3 - the components of 1 ?

I must finish this soon thanks for the help in advance

2. Jun 30, 2011

### azureth

the equation represents the position vector in the form of coordinates.make t=1and t=3,you will get two position vectors (-5,10,5)and(-15,90,-20).use the knowledge of vector of the form of coordinates and you will get the answer

3. Jun 30, 2011

### Jimmy84

Now I must only get the magntitude of the vectors? thanks

4. Jun 30, 2011

### azureth

you may get the magnitude of the vector of displacement by using pythagorean theorem

5. Jun 30, 2011

thanks a lot