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**Quick "Equations of Motion" questions (2). Rxn time; deceleration**

**1. A meteorite strikes on October 9, 1992, a 27-pound meteorite struck a car in Peekskill, NY, leaving a dent 22 cm deep in the trunk. If the meteorite struck the car with a speed of 130 m/s, what was the magnitude of its deceleration, assuming it to be constant?**

27# meteorite

22cm dent in trucnk

130 m/s

## Homework Equations

v^2=v0^2+2a(x-x0)=v0^2+2a(change in)x

v=-22

v0=130m/s

a=? (to be solved for)

x=?

x0=?

I'm pretty sure this is not the equation since distance is not given.

## The Attempt at a Solution

I'm lost without the correct equation... :(

**1. You are driving through town at 16 m/s when suddenly a car backs out of a driveway in front of you. you apply brakes and begin decelerating at 3.2 m/s^2.**

c. If the car backing out was initially 55 m in front of you, what is the maximum reaction time you can have before hitting the brakes and still avoid hitting the car?

c. If the car backing out was initially 55 m in front of you, what is the maximum reaction time you can have before hitting the brakes and still avoid hitting the car?

v0=16m/s

a=-3.2 m/s^2

(change in)x=55 m

v=0

## Homework Equations

[(change in)x=v^2-v0^2]/[2a]

v=v0+at=0

## The Attempt at a Solution

0=16m/s+(-3.2m/s^2)t

t=5s?

answer given is 0.945s, but i want to learn how to get there.

Thanks for looking!

Steve

If I could just get an equation, that would help greatly!

Thanks again!