Question

Mike and John challenge each other to a 100 m race across the football field. The loser will grade the winner's physics labs for one month. John runs the race at a steady 8 m/s and finishes in 12.5 s. Mike runs for 4 seconds with a speed of 10 m/s. Huffing and puffing, he then stops for 3 seconds. With a last burst, he finishes the race with a speed of 12 m/s. What is Mike's time for the race?

Answer 1

Mike's total time for the 100 m race is calculated by adding the time taken for each stage of the race, which results in a total time of 12 seconds.

Step-by-step explanation:

To determine Mike's time for the race, we can calculate the distance he covers at each stage of his race and the time he takes. Mike has three distinct stages during the race:

• Stage 1: Mike runs at 10 m/s for 4 seconds. Distance = speed × time = 10 m/s × 4 s = 40 m.
• Stage 2: Mike stops for 3 seconds, covering 0 meters.
• Stage 3: The remaining distance Mike has to cover is 100 m - 40 m = 60 m. Mike runs this last stretch at 12 m/s.

Time for stage 3 = distance ÷ speed = 60 m ÷ 12 m/s = 5 seconds.

Adding the times for each stage:

• Stage 1: 4 seconds
• Stage 2: 3 seconds
• Stage 3: 5 seconds

Total time for Mike's race: 4 s + 3 s + 5 s = 12 seconds.