Is this the correct formula that im using for this question?

[ImsoFly]

1. Homework Statement
hi this is the problem: the burning of the second stage of a two stage toy rocket takes the rocket from 12 m/s to 40 m/s in 5.0s. How far does the rocket during this time?


2. Homework Equations
would i use delta t= delta v/a ? would the given info be.. delta v1= 17 m/s, delta v2=40m/s and delta t=5.0s... if this isn't the correct formula please correct me. thank u all!

 

[misterme09]

distance = (1/2)*a*t^2 + vi*t

where a = delta v / delta t

and vi is the initial velocity (12 m/s)

 

[ImsoFly]

distance = (1/2)*a*t^2 + vi*t

where a = delta v / delta t

and vi is the initial velocity (12 m/s)

but the question asks for time

 

[cristo]

but the question asks for time

No it doesnt.. it asks for distance! Firstly, work out the acceleration using your equation, then plug this along with initial velocity and time into the equation for distance given in post #2.

 

[ImsoFly]

No it doesnt.. it asks for distance! Firstly, work out the acceleration using your equation, then plug this along with initial velocity and time into the equation for distance given in post #2.

what do you mean by working out the acceleration?

 

[cristo]

what do you mean by working out the acceleration?

sorry, you'll just be going round in circles by doing that! you can use another of the "kinematic equations", namely $$d=\frac{v_i+v_f}{2}\cdot t$$.

Here's a link to the kinematic equations http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/1DKin/U1L6a.html . These equations are normally the tools you need for questions involving a constant acceleration.

 

[ImsoFly]

sorry, you'll just be going round in circles by doing that! you can use another of the "kinematic equations", namely $$d=\frac{v_i+v_f}{2}\cdot t$$.

Here's a link to the kinematic equations http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/1DKin/U1L6a.html . These equations are normally the tools you need for questions involving a constant acceleration.

kk, thanks a bunch