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An airplane decelerates uniformly from 140 m/s to 70 m/s and travels 1700 m while doing so. What s the time interval for the deceleration?
1 Answer
- donpatLv 76 years agoFavorite Answer
You have :
------------------
a = dv/dt = ad ------> dt = dv/ad
v = ds/dt ---------------> dt = ds/v
dt = dv / ad = ds/v
v dv = ( ad ) ds
[ 1/2] [ ( v70 )^2 - v140 )^2 ] = [ ad ] [ Delta s ]
dv = ( ad ) dt
v70 - v140 = ( ad ) ( td )
ad = [ ( 70 m/s )^2 - ( 140 m/s )^2 ] / [ ( 2 ) ( 1700 m ) ]
ad = - 5.765 m/s^2
v70 = v140 - ( ad ) ( td )
td = ( v70 - v140 ) / ( ad )
td = ( 70 m/s - 140 m/s ) / ( - 5.765 m/s^2 )
td = 12.14 s <------------
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