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lianna [129]
3 years ago
9

5. A car is making a 12-mile trip. It travels the first 6.0 miles at 30 miles per hour and the last 6.0 miles at 60 miles per ho

ur. What is the car's average speed for the entire trip? A) 20 mph B) 35 mph C) 40 mph D) 45 mph E) 50 mph
Physics
1 answer:
stellarik [79]3 years ago
5 0

Answer:C

Explanation:

Given

Total distance covered by car d=12\ miles

First it travels d_1=6\ miles with v_1=30\ mph

then it travels d_2=6\ miles with v_2=60\ mph

time taken during first half t_1=\frac{d_1}{v_1}=\frac{6}{30}=0.2\ hr

time taken during Second half t_1=\frac{d_2}{v_2}=\frac{6}{60}=0.1\ hr

average speed v_{avg}=\frac{distance}{time}

v_{avg}=\frac{12}{0.2+0.1}=\frac{12}{0.3}=40\ mph

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