Finding how long it takes given changing acceleration

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To determine the time required for an automobile to accelerate from 72.0 km/hr to 100.0 km/hr with an acceleration of 1.57 m/s², the equation vf = vi + at is used. The initial velocity (vi) is converted to meters per second, resulting in a change of 28 m/s. The calculation shows that the time (t) needed for this acceleration is approximately 17.83 seconds. It is emphasized to be cautious with unit conversions, either converting km/hr to m/s or m/s² to km/hr². Accurate unit handling is crucial for correct results in physics problems.
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Homework Statement


At highway speeds, a particular automobile is capable of an acceleration of about 1.57 m/s2. At this rate, how long does it take to accelerate from 72.0 km/hr to 100.0 km/hr?


Homework Equations



I was given: vf = vi + at

The Attempt at a Solution



Simplifying the velocities I got 28 = 1.57a
and a= 17.83 s.
 
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lim said:

Homework Statement


At highway speeds, a particular automobile is capable of an acceleration of about 1.57 m/s2. At this rate, how long does it take to accelerate from 72.0 km/hr to 100.0 km/hr?


Homework Equations



I was given: vf = vi + at

The Attempt at a Solution



Simplifying the velocities I got 28 = 1.57a
and a= 17.83 s.

careful about units... convert km/hr to m/s or convert m/s^2 to km/hr^2...
 

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