help A hare and a tortoise compete in a race over a straight course 1.05 km long

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A hare and a tortoise compete in a race over a straight course 1.05 km long. The tortoise crawls at a speed of 0.140 m/s toward the finish line. The hare runs at a speed of 8.30 m/s toward the finish line for 0.840 km and then stops to tease the slow-moving tortoise as the tortoise eventually passes by. The hare waits for a while after the tortoise passes and then runs toward the finish line again at 8.30 m/s. Both the hare and the tortoise cross the finish line at the exact same instant. Assume both animals, when moving, move steadily at their respective speeds. How far is the tortoise from the finish line when the hare resumes the race? For how long in time was the hare stationary? A 47.5-g Super Ball traveling at 27.0 m/s bounces off a brick wall and rebounds at 20.5 m/s. A high-speed camera records this event. If the ball is in contact with the wall for 4.70 ms, what is the magnitude of the average acceleration of the ball during this time

Explanation / Answer

A) hare takes (1.05-0.84)*10^3/8.3s= 25.3s. so the tortoise was 0.14*25.3m=3.54m away from finish line

B)total race time= 1.05*10^3/0.14=7500s.before stopping hair runs for 0.84*10^3/8.3= 101.2 s. so he stps for 7500-101.2-25.3= 7373.5s.........(ans)

change of velocity=27-(-20.5)=47.5 m/s

so acceleration= 47.5/(4.7*10^-3)=10106.38 m/s^2

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