Find deceleration from distance and initial velocityby physicsnnewbie Tags: deceleration, distance, initial, velocity 

#1
Dec3110, 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. 



#2
Dec3110, 03:01 AM

HW Helper
P: 6,213

solve for t using the quadratic equation formula.




#3
Dec3110, 05:49 AM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 38,890

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. 



#4
Dec3110, 08:48 AM

P: 49

Find deceleration from distance and initial velocity
Thanks Ivy, don't know why I didn't think of that.



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