Posted by Bob on Sunday, October 3, 2010 at 3:57pm.
To stop a car, you require first a certain reaction time to begin braking. Then the car slows under the constant braking deceleration. Suppose that the total distance moved by your car during these two phases is 56.7 m when its initial speed is 80.0 km/h, and 24.4 m when the initial speed is 47.8 km/h.
(a) What is your reaction time?
(b) What is the magnitude of the deceleration?
I tried eliminating the values in order to find accel and time, but the values canceled out and when I tried separating them, I got the answer wrong. What am I doing wrong?

Physics  bobpursley, Sunday, October 3, 2010 at 4:07pm
I don't see how it is solvable, unless you assume the acceleration is different on each, or the time during deacceleartion is the same.
You have as variables: a, time to slow, tr.

Physics  Bob, Sunday, October 3, 2010 at 4:22pm
Let me try to clarify
v1=22.222 m/s
v2=13.278 m/s
x=vi(t)+1/2a(t^2)
56.7=22.222t+1/2a(t^2)
24.4=13.278t+1/2a(t^2).
Through elimination
32.3=8.94t
t=3.611s
From there I separated to vi=at as vf is 0
22.222=a(3.611)
13.278=a(3.611)
35.5=7.222a
a=4.92 m/s^2

Physics  Bob, Sunday, October 3, 2010 at 4:30pm
Forgot to put my question at the end of it XD
This is from me trying to interpret what you've done in the previous times this question has been asked, but obviously, I'm wrong somewhere. At what point in the work am I messing up?

Physics  John, Monday, August 15, 2016 at 4:36pm
2.53 seconds
Answer This Question
Related Questions
 AP Physics  To stop a car, you require first a certain reaction time to begin ...
 Physics  To stop a car, first you require a certain reaction time to begin ...
 Physics  A driver in a car, originally moving at 13.1 m/s, applies the brakes ...
 Physics  Proper design of automobile braking systems must account for heat ...
 physics  Proper design of automobile braking systems must account for heat ...
 Physics  A CAR HAS A MASS OF 1200KG TRAVELLING ON A LEVEL ROAD. THE CAR ...
 Physics  The braking distance of a car is 29m. If the speed of the car is ...
 Physics  You are driving down the highway late one night at 20 m/s when a deer ...
 college math  Braking distance The braking distance y in feetthat it takes for ...
 physics  Proper design of automobile braking systems must account for heat ...
More Related Questions