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physicshelpme

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**problem does not make sense km/h at m/s??**

**1. A van is traveling at 80 km/h at 25 m/s undergoes uniform deceleration when the brakes are applied, slowing to 50 km/h at 10 m/s after 2.1 s. (a) what is the deceleration? (b) How far does it travel during this period? (c) How much farther does it travel before stopping if deceleration remains constant?**

Variables= i don't understand what is meant by 80km/h at 25m/s and 50km/h at 10m/s

vi=25m/s? vf=10m/s? t=2.1s 1)find=-a? 2)displacement=? 3)at vf=0 displacement?

1)i used d=(vi+v2)/2 x t

2)vf=vi+at to find acceleration

3)know how to compute but didnt because I am unsure of my answer what to do with 80km/h what does this mean? please help

d=37m

a=-7.14m/s^2

Variables= i don't understand what is meant by 80km/h at 25m/s and 50km/h at 10m/s

vi=25m/s? vf=10m/s? t=2.1s 1)find=-a? 2)displacement=? 3)at vf=0 displacement?

## Homework Equations

1)i used d=(vi+v2)/2 x t

2)vf=vi+at to find acceleration

3)know how to compute but didnt because I am unsure of my answer what to do with 80km/h what does this mean? please help

## The Attempt at a Solution

d=37m

a=-7.14m/s^2