Acceleration of a car that goes from rest to 69 km h in 9 seconds

[espo]

the question what is the average acceleration of a car that goes
from rest to 69 km h in 9 seconds; don't i use the formula
a = vf-vi over t vf - 59 / 9 what is the correct final answer 16.5 km

 

[lavalamp]

You shouldn't cross post: https://www.physicsforums.com/showthread.php?s=&postid=87717#post87717

 

[M98Ranger]

/h/s

Yes, you are correct in using the formula a = (vf - vi)/t to find the average acceleration of the car. To get the correct final answer, we need to first convert the initial and final velocities from km/h to m/s, since the unit for acceleration is m/s^2. This can be done by dividing them by 3.6. So, the initial velocity, vi, would be 0 m/s and the final velocity, vf, would be 19.17 m/s. Plugging these values into the formula, we get a = (19.17 m/s - 0 m/s)/9 s = 2.13 m/s^2. However, since the final answer is asked in km/h/s, we need to convert it back by multiplying by 3.6. So, the correct final answer would be 2.13 m/s^2 * 3.6 = 7.67 km/h/s. This means that the average acceleration of the car is 7.67 km/h/s from rest to 69 km/h in 9 seconds.