# Acceleration, Solve for time (Algebra Based)

by Dig
Tags: acceleration, algebra, based, solve, time
 P: 13 1. The problem statement, all variables and given/known data 22. The average person passes out an acceleration of 7g (that is, seven times the gravitational acceleration on Earth). Suppose a car is designed to accelerate at this rate. How much time would be required for the car to accelerate from rest to 60.0 miles per hour? (The car would need rocket boosters!) 2. Relevant equations 3. The attempt at a solution v1 = 60 v0 = 0 a = 7 * 9.8 => 68.6m/s^2 a = change in velocity/change in time So, 68.6m/s^2 = 60mph/t 68.6 * t = 60mpg t = 60/68.6 = 0.87 seconds I am not sure if this is correct or not. The answer seems within reason since a very high powered sports car accelerates from 0-60 miles per hour in around 3 seconds, so 0.87 seconds would line up well with the exaggeration of the speed of the car mentioned at the end of the word problem. Any help is appreciated :).
 P: 117 You are mixing English and SI units.
P: 13
 Quote by edziura You are mixing English and SI units.
Care to elaborate on where I went wrong and what I can do to correct my problem?

 P: 180 Acceleration, Solve for time (Algebra Based) Dig. What he/she meant was that you are using G's (or 9.8m/s2) which is the acceleration on earth in metric, and then Miles per hour, which is SI. To fix this, take the MPH and multiply by .44 (or to be more exact, .44704) to get meters/second By the way, the way to get the .44 is roughly 1600 meters/3600seconds = .44 (mile/hour hour=60 minutes=60 seconds. so 60[SUP]2[SUP]) This should give you some help, or at least point you in the correct direction. Your equation is correct though.
P: 13
 Quote by lax1113 Dig. What he/she meant was that you are using G's (or 9.8m/s2) which is the acceleration on earth in metric, and then Miles per hour, which is SI. To fix this, take the MPH and multiply by .44 (or to be more exact, .44704) to get meters/second By the way, the way to get the .44 is roughly 1600 meters/3600seconds = .44 (mile/hour hour=60 minutes=60 seconds. so 60[SUP]2[SUP]) This should give you some help, or at least point you in the correct direction. Your equation is correct though.
Alright, if I multiply 60mi/h by .44, I receive 26.4m/s. I divide this by 68.6m/s^2 to get an answer of .385s? Both the numerator and denominator have 3 significant digits, so I stop at .385 correct?

I see my mistake now. Thank you both for pointing that out to me.
 P: 180 No problem Dig, That seems correct to me. Good luck in physics this year.
P: 13
 Quote by lax1113 No problem Dig, That seems correct to me. Good luck in physics this year.
Thank you so much :).

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