# How to solve for Initial velocity Problem

## Homework Statement

A bobsled glides down a hill with an acceleration of -4.5 m/s If it stops after 5 s, what was its initial velocity?

2. Homework Equations

i know vf(final)= v + at

## The Attempt at a Solution

i multiplied -4.5m/s by 5s and i got the correct answer the only problem is the answer is negative, i need it to be positive. Where or what did i do wrong?

NascentOxygen
Staff Emeritus
Science Advisor

## Homework Statement

A bobsled glides down a hill with an acceleration of -4.5 m/s If it stops after 5 s, what was its initial velocity?

2. Homework Equations

i know vf(final)= v + at

## The Attempt at a Solution

i multiplied -4.5m/s by 5s and i got the correct answer the only problem is the answer is negative, i need it to be positive. Where or what did i do wrong?
Write the equation you are using to solve this problem, then substitute in it for the variables you know.

The issue is I do not know what equation to use. I though the initial velocity equation would help, but I am not given final velocity I only have two known variables

NascentOxygen
Staff Emeritus
Science Advisor
The problem states clearly what the sled's final speed is. The unknown here is its initial speed.

so distance over time ?

i know the equation for for final velocity is vf= v(initial) + (a)(t)<---- acceleration multiplied by time

to get the final velocity i did do distance over time giving me -0.9 then i multiplied -4.5m/s by 5s i added all those figures together giving me a number that is not similar to the answer key

NascentOxygen
Staff Emeritus
Science Advisor
The sled is brought to a stop, which tells you its final speed is 0 m/s.

• pennywise1234
o damn, right under my nose.