Register to reply

Find deceleration from distance and initial velocity

by physicsnnewbie
Tags: deceleration, distance, initial, velocity
Share this thread:
physicsnnewbie
#1
Dec31-10, 02:49 AM
P: 49
I have just started a calculus book, and I cant figure out how to solve this problem:

1. The problem statement, all variables and given/known data
The landing velocity of an airplane (i.e., the velocity at which it touches the ground) is 100 mi/hr. It decelerates at a constant rate and comes to a stop after traveling 1/4 mile along a straight landing strip. Find the deceleration or negative acceleration.



2. Relevant equations



3. The attempt at a solution
a = x
v = xt + C
v = xt + 100
s = (x/2)t^2 + 100t + C
1/4 = (x/2)t^2 +100t

I'm not sure what to do next.
Phys.Org News Partner Science news on Phys.org
Hoverbike drone project for air transport takes off
Earlier Stone Age artifacts found in Northern Cape of South Africa
Study reveals new characteristics of complex oxide surfaces
rock.freak667
#2
Dec31-10, 03:01 AM
HW Helper
P: 6,208
solve for t using the quadratic equation formula.
HallsofIvy
#3
Dec31-10, 05:49 AM
Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 39,315
Quote Quote by physicsnnewbie View Post
I have just started a calculus book, and I cant figure out how to solve this problem:

1. The problem statement, all variables and given/known data
The landing velocity of an airplane (i.e., the velocity at which it touches the ground) is 100 mi/hr. It decelerates at a constant rate and comes to a stop after traveling 1/4 mile along a straight landing strip. Find the deceleration or negative acceleration.



2. Relevant equations



3. The attempt at a solution
a = x
v = xt + C
v = xt + 100
s = (x/2)t^2 + 100t + C
1/4 = (x/2)t^2 +100t

I'm not sure what to do next.
In addition to 1/4= (x/2)t^2+ 100t, which says that the airplane moved 1/4 mile in t hours, you have xt+ 100= 0 since the airplane came to a stop (has speed 0) in that time.
From xt= -100, x= -100/t.

Replace x in 1/4= (x/2)t^2+ 100t with that and solve the resulting linear equation for t. Once, you have t, you can solve for x from x= -100/t.

physicsnnewbie
#4
Dec31-10, 08:48 AM
P: 49
Find deceleration from distance and initial velocity

Thanks Ivy, don't know why I didn't think of that.


Register to reply

Related Discussions
Find initial velocity given angle and distance to go over an object Introductory Physics Homework 15
How to find the initial velocity given only angle and distance traveled Introductory Physics Homework 9
Find initial Velocity with only distance, angle, and acceleration. Introductory Physics Homework 5
Find Initial Velocity given angle, distance, height launched from. Introductory Physics Homework 1
Given angle and distance traveled find initial velocity Introductory Physics Homework 3