Question

At t = 0, a car registers at 30 miles/hr. Forty seconds later, the car’s velocity is now at 50 miles/hr. Assuming constant acceleration, what is the distance covered after 40s?
Select one:
a. 0.442 mi
b. .33 mi
c. 0.11 mi
d. 10.33
e. None of the choices given.

Answer 1

Answer: Choice A) 0.44 miles

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Work Shown:

1 hour = 60 minutes

1 minute = 60 seconds

1 hour = 60*60 = 3600 seconds

40 seconds = 40*(1/3600) = 40/3600 = 1/90 hours

The car travels 1/90 of an hour. Let t = 1/90.

The initial velocity is vi = 30 mph.

The final velocity is vf = 50 mph.

Apply one of the kinematics equations as given below.

x = distance traveled

x = 0.5*(vi+vf)*t

x = 0.5*(30+50)*(1/90)

x = 0.44444444444444 which is approximate

x = 0.44

The car traveled roughly 0.44 miles. This matches with choice A.

I'm assuming choice A is supposed to say 0.44 instead of 0.442; otherwise, I think your teacher made a typo by putting that 2 in there. Each of the other answer choices are accurate to 2 decimal places, so it would make sense that choice A is also accurate to 2 decimal places as well.

If 0.442 was intended by your teacher, and it's not a typo, then the answer would be E) None of the choices given.