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i got this question in my first assignment in PHYS 109. i am sure the question is easy, but for some reason i can't get it around my head.

Thanks for the help !!

1. The problem statement, all variables and given/known data

Code (Text):A physics 109 student is taking a car for a joy ride on a long, empty and perfectly

straight Saskatchewan highway. At the beginning of the joy ride the student has the

car accelerate from rest to some top speed with a (constant) acceleration of 4:50 m=s2

and then maintains that top speed to the end of the ride. The total time taken from

the start of the joy ride to its end is 1:36 minutes and the total distance covered is

3:84 km.

(a) What was the time elapsed during the acceleration phase of the car's motion?

(b) What distance did the car cover during the acceleration phase of its motion?

(c) What was the top speed reached by the car?

2. Relevant equations

V = Vi +at

Xf=Xi +Vi(t) + (1/2)(a)(t^2)

V=(Vf+vi)/2

3. The attempt at a solution

Givens:

a=4.50

t=81.6 s

Xf =3.84 * 10^3 m

a) Vavg. = X/t = 3480/81.6 = 47.1 m/s

Vavg= (Vf + Vi)/2

=> Vf= 2(Vavg - Vi)

==>Vf= 2(47.1 -0)= 94.1 m/s

Vf=at +Vi

=>t=(Vf - Vi)/a = 20.9 s

b)

Xf=Xi +Vi(t) + (1/2)(a)(t^2)

Xf= 0+0+(0.5)(4.50)(20.9^2) = 982.8m

C)Vf = 94.1 m/s

i dont belive in my answer because :

1) The top speed is 339 KM/h....yes it is possible, but he must be one rich Phys student we are talking about here

2) I got the Vf in the very bigening, yet he asks me about it at the end ? then i must be doing somethiong wrong

Thank you guys, anhy help is really appreciated

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# Homework Help: Acceleration in a joy ride

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