Calculating Acceleration with Known Velocity and Distance - Homework Problem

[Speedking96]

Homework Statement

An object takes 1.20 seconds to reach a velocity of 12.6 m/s. What is its acceleration if it covered 11.34 meters?

Homework Equations

Vf ^2 = Vi ^ 2 + 2ad

The Attempt at a Solution

Well, I am not sure if the initial velocity is zero or if it is starting at some velocity x.

My attempt:

12.6^2 = 0^2 + 2(a)(11.34)

a = 7 m/s^2

I know this is wrong but I don't understand how to solve it if I don't know what the initial velocity is?

Thank you.

 

[Speedking96]

I would be really glad if someone could quickly explain this to me because I am having a hard time with acceleration problems. Thank you.

 

[gneill]

Looks like you'll need to solve more than one equation. Write separate equations for the distance covered and the final velocity given that there is an initial velocity. Two equations, two unknowns. You only need to find one of them (a).

 

[Speedking96]

12.6 ^2 = Vi ^2 + (2)(a)(11.34)

12.6 = Vi + a (1.2 seconds)

After substituting Vi from equation 2 into equation number 1, I find that the acceleration is 4.25m/s/s.

THANK YOU THANK YOU THANK YOU.

 

[gneill]

12.6 ^2 = Vi ^2 + (2)(a)(11.34)

12.6 = Vi + a (1.2 seconds)

After substituting Vi from equation 2 into equation number 1, I find that the acceleration is 4.25m/s/s.

THANK YOU THANK YOU THANK YOU.

Maybe a typo, but check your acceleration value. 4.25?

 

[Speedking96]

Maybe a typo, but check your acceleration value. 4.25?

Woops. It's 5.25 m/s/s.

 

[iRaid]

a=v/t with that you have the time then plug it into another equation.

 

[gneill]

Woops. It's 5.25 m/s/s.