80. The distance, d, traveled by an automobile moving at an average speed of s i

Question

80. The distance, d, traveled by an automobile moving at an average speed of s is directly proportional to the time, t, spent traveling. The proportionality constant is the average speed (a) Express this proportionality in mathematical form. (b) If it takes the automobile 3.88 hours to travel a distance of 239 miles, what are the value and units of the proportionality constant? (c) Assuming the same average speed as in part (b), how long will it take the automobile to travel a distance of 659 miles? 81. It takes 7.39 kilocalories to melt 92 grams of ice. Calculate the heat of fusion of water. (See Question 79. Careful on the units the answer will be in calories per gram.)

Explanation / Answer

80)

(a) Since the distance (d) is proportioanl to the time (t),

Methametical form is d = s*t

Here, s is the proportionality constant and is equal to the average speed.

(b) s = d/t

Given d is 239 miles and t is 3.88 hours

s = 239 miles/3.88 hours = 61.6 miles per hour

(c): s = 61.6 miles per hour and d is 659 miles.

t = d/s = 659 miles/(61.6 miles per hour) = 10.69 hours = 10.7 hours.

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