How to solve for Initial velocity Problem

Click For Summary

Homework Help Overview

The discussion revolves around a physics problem involving a bobsled that accelerates down a hill with a specified negative acceleration and comes to a stop after a certain time. Participants are tasked with determining the initial velocity of the bobsled.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the use of the equation relating final velocity, initial velocity, acceleration, and time. Some express confusion about the signs of their calculations and the implications of the sled coming to a stop.

Discussion Status

There is an ongoing exploration of the correct application of the relevant equations. Some participants have pointed out the final velocity of the sled is zero, which has prompted others to reconsider their understanding of the problem setup.

Contextual Notes

Participants note the challenge of working with negative acceleration and the implications it has on the interpretation of initial velocity. There is also mention of the need for clarity regarding the final velocity in the context of the problem.

pennywise1234
Messages
44
Reaction score
0

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?
 
Physics news on Phys.org
pennywise1234 said:

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
 
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
 
The sled is brought to a stop, which tells you its final speed is 0 m/s.
 
  • Like
Likes   Reactions: pennywise1234
o damn, right under my nose.
 

Similar threads

projectile motion problem with no initial velocity given
  • · Replies 3 ·
Replies
3
Views
997
Projectile motion, initial height and range given, find initial velocity
  • · Replies 8 ·
Replies
8
Views
2K
Projectile Motion Problem Involving Initial Velocity and Gravity Only
  • · Replies 11 ·
Replies
11
Views
2K
Trying to Calculate Initial Velocity and Final Velocity
  • · Replies 2 ·
Replies
2
Views
930
Why do I keep getting friction coefficient as a negative?
  • · Replies 17 ·
Replies
17
Views
3K
Determine initial velocity of a vertical throw
  • · Replies 11 ·
Replies
11
Views
4K
Initial velocity of bird landing on horizontal wire modeled as spring
  • · Replies 7 ·
Replies
7
Views
1K
Ambiguous question on momentum and how it works...
  • · Replies 13 ·
Replies
13
Views
1K
Find the value of ##T## and distance of particle in the first ##4## seconds
  • · Replies 2 ·
Replies
2
Views
1K
Projectile Motion: initial velocity problem
  • · Replies 1 ·
Replies
1
Views
2K