# Homework Help: Kinematics question on brakes

1. Aug 29, 2006

### konichiwa2x

Hi, can someone please check if this is right?

A driver applies brakes on seeing a traffic signal 400m ahead. At the time of applying the brakes, the vehicle was moving with 15m/s and retarding with 0.3m/s^2. What is the distance of the vehicle from the traffic light after 1 minute?

x = 15(60) - 1/2(0.3)(60)^2
x = 360m

Therefore the distance from the traffic light is 40m. Correct?
My book says the answer is 25m. Is it wrong? Any help will be appreciated.Thanks!

2. Aug 29, 2006

### dmoravec

I can't see anything wrong with your work. Either the book is wrong or we're both reading the question wrong (ie: the driver starts breaking after 1 second and then breaks for a minute)

3. Oct 28, 2009

### paras3017

hey BOY,
SEE the driver has applied brakes so just calculate the time the car ll take to stop by the eq. v=u+at.Then just calc the dis by eq s=ut+1/2at^2....the dis ll be 375m.so dis from traffic light is 400-375 i.e 25 m dear.
PARAS sir
SUNITI CLASSES
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