Finding the initial velocity, .

[megkirch]

Homework Statement

The position x of an object as a function of time is given as x = 2.257 + 4.894 t + 16.5 t2. All quantities are understood to be quoted in SI units. What is the initial velocity ? Indicate with a negative (positive) sign whether the acceleration is constant (not constant) for the given expression.

Homework Equations

i think i have to use. x=x0+v0(t)+1/2(a)t^2)

The Attempt at a Solution

the problem is confusing me becuase I am not sure what numbers should go where in the equation. i know the initial velocity is v0.

 

[olivermsun]

So can you compare the equation you wrote in (2) with the one you wrote in (1)?

 

[megkirch]

2.257 would be the x0, 4.894 would be the t, and 16.5 would go where the t^2 is. I am not sure what to put as the a.

 

[tiny-tim]

welcome to pf!

hi megkirch! welcome to pf!

2.257 would be the x0, 4.894 would be the t

yes

… , and 16.5 would go where the t^2 is. I am not sure what to put as the a.

16.5 is the ½a

 

[megkirch]

ohh ok thank you! So it would be, x=2.257+V0(4.894)+1/2(16.5)?

 

[tiny-tim]

ohh ok thank you! So it would be, x=2.257+V0(4.894)+1/2(16.5)?

i hesitate to dampen your enthusiasm, but that doesn't really make any sense :tongue2:

would you like to rephrase it? ​

 

[megkirch]

do i have that equation set up right?

 

[megkirch]

i have been stuck on this one problem all day, please help.

 

[Rayquesto]

What I would do is derive the equation using nx^n-1 where n represents the power in terms of time and you will get the equation that represents velocity.

from this equation, v= v0 + at, what can you say about v0 in the equation that you derived. (hint: the derived equation is identical to the velocity equation)

 

[tiny-tim]

do i have that equation set up right?

the equation is x = 2.257 + 4.894 t + 16.5 t²

you have to find v₀ and a …

so what is a?​

 

[megkirch]

sorry, I am completely lost

 

[Rayquesto]

do you know how to find a derivative?

 

[megkirch]

yes the derivative of the equations is. 2.257=0 4.894t=4.894 16.5t^2=33.

 

[megkirch]

thank you so much! i finally got the answer its 4.894

 

[Rayquesto]

thats what I think :) want a second opinion? I mean I'm sure that's right.

 

[megkirch]

my homework is online it said its right. thank you again