i need to find the speed of acceleration

[lookagain]

post 15 told me divide 10 intervals to find the distance. why my calculation is wrong? how to find the speeds of 10 intervals given in post 16?

Please ignore that part of post 15. I tried to post a correction a couple of days
ago, but the site would not accept my post so I gave up.

 

[lookagain]

in post 24, he say the distance is 292 feet? how? i can't find this distance

No, I stated that 292 feet is an upper bound, and that it is not the answer.

 

[logistic_guy]

thank you. i'll try to figure a way

 

[khansaheb]

this is the question

Suppose that a car can accelerate from 30 mph to 50 mph in 4 seconds. Assuming a constant acceleration, find the acceleration (in miles per second squared) of the car and find the distance traveled by the car during the 4 seconds.

the FIND of the problem is "distance" traveled.

Given of the problem is:

Initial velocity = 30 mph = u

final velocity = 50 mph = v

elapsed time = 4 sec = 1/900 hour = t

Assume linear motion and constant acceleration - then we can use Galileo's equations (a = acceleration and s = distance traveled)- which are:

v = u + a*t............................(1)

s = u*t + (1/2) * a * t^2.........(2)

v^2 = u^2 + 2 * a * s ...........(3)

Looking at these equations (and other givens) - we formulate our strategy:

using equation (1) we get,

a = (v - u)/t = 18000 mph^2 ....................(be very cognizant about the units in these problems)

then we use equation (3), to get,

s = (v^2 - u^2)/(2*a) ................................complete it using the given and the calculated data. Be careful about the unit of 's'.

and the FIND is found!

 

[logistic_guy]

thank you

Assume linear motion and constant acceleration - then we can use Galileo's equations (a = acceleration and s = distance traveled)- which are:

if this said in post 2, i save lots of time. i think i am understanding now

 

[khansaheb]

if this said in post 2

We were hoping that you would know the assumptions used in deriving those equations.

Anyway, now you know

Why the equations (stated in the book) are re-derived in the classroom and​

the assumptions are re-stated.​

Knowing this now will save you lots of time in the future.

 

[logistic_guy]

yes thank you