Question

A car traveling 40 mi/h accelerates uniformly
for 5.3 s, covering 551 ft in this time.
What was its acceleration?
Answer in units of ft/s
2

Ive gotten a=12.05 and 14.34 but neither of those are right.

Answer 1

Did you convert your velocity from mi/h to ft/s correctly?
There are 5280 ft/mi and 3600 s/h.

Answer 2

40m/h = 58.7ft/s

This is my way of doing this:

v^2 = (v initial)^2 + 2as

(58.7ft/s)^2 = 0 + 2a(551ft)

3442ft2/s2 = (1102ft)a

=> a = 3.12ft/s^2

Answer 3

thats not the answer, i assumed we dont know final velocity, so i have initalv= 40mi/h, time=5.3seconds and d=551ft. I think i must use the equation d=vi*t+.5(a)(t)^2 but nothing i get is right.

Answer 4

what is the right answer that's written in your textbook?

Answer 5

its an online assignment so i dont know the right answer, it just lets me know if it is wrong. I know for sure thats the equation i use because the next question of the assignment asks what is the final velocity.

Answer 6

can you try 17.1m/s2 to see if it's correct?

Answer 7

i mean ft

Answer 8

YES! thats right!, thank you!

Answer 9

nice! Just thought you should know I use the formula d = di + vi*t + 1/2at^2
=> 551 = 0 + 5.3*58.7 + 1/2a(5.3)^2
=> 551 = 311 + 14a
=> a = 17.1 ft/s2

Answer 10

to find the final velocity do i use the equation, a=vf-vi/t ?

Answer 11

yes. Be careful. use 58.7ft/s instead of 40mi/h

Answer 12

Thanks so much for all your help, have a good night! ... or day dependning on where you are!