You are in bozeman. you start your parked car, drive to Three Forks, stop for a

Question

You are in bozeman. you start your parked car, drive to Three Forks, stop for a 1 hour coffee break, and arrive and park in Helena exactly 2 hours after leaving Bozeman. Since it is 100 miles from Bozeman to Helena, the average speed of the trip is 50 mph. Which of the following statements about this trip is correct?

(A) To average 50 mph the car must have exceeded 100 mph for at least 60 minutes of the trip.

(B) The instantaneous speed was never equal to 50 mph during this trip.

(C) You can never average 50 mph if the speed is zero for one half of the trip duration.

(D) None of the statements (A), (B), and (C) are correct.

(E) (A), (B), and (C) are all corect.

Explanation / Answer

So basically in 2 hrs, there is a 1 hour coffee break,
Therefore, 100 miles is coverd in 1 hr ,

Vavg = 100/1 = 100 miles/hr

(A) If the car exceeds100 mph for at least 60 minutes of the trip, the avg would be more !! False

(B) The instantaneous speed was never equal to 50 mph during this trip. :- False, if it has to reach higher speed , it should surpass 50 mph limit once in the trip , and second time while slowing down !!

(C) You can never average 50 mph if the speed is zero for one half of the trip duration. :- This is false, we can if we move at much higher speed !!

Correct option :- (D) None of the statements (A), (B), and (C) are correct.

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