Young Jeffrey is bored, and decides to throw some things out of the window for f

Question

Young Jeffrey is bored, and decides to throw some things out of the window for fun. But since he is also very curious, he decides to do so in a controlled way. Jeffrey takes a rock, his tennis ball, and one of his father's golf balls and sets them on the sill of an open window. Then he uses a flat board to carefully push them all out of the window at the same time. The 2nd story window is 11.0 feet above the ground, and all three objects hit the ground just 0.950 feet away from the base of the house at the same time, 0.827 seconds after they're dropped. The rock hits with a thud and stays put, but the other two objects bounce. After another 0.620 seconds, the tennis ball reaches a maximum height of 6.19 feet, while the golf ball is 8.66 feet off the ground and still rising. Both have travelled an additional 0.713 feet horizontally. Calculate the magnitude of the average velocity of each object during these 1.45 seconds. Which object has the largest instantaneous velocity at the end of this time period?

Explanation / Answer

displacement of the rock vertically = 11ft

displacement of the rock horizontally = 0.950ft

displacement of the rock = sqrt(112 +0.952)=11.041ft

average velocity of the rock =displacement of the rock /time taken = 11.041ft/0.827s=13.351 ft/s

displacement of the tennis ball vertically = 11ft-6.19ft = 4.81ft

displacement of the tennis ball horizontally = 0.950ft+0.713ft = 1.663 ft

displacement of the tennis ball = sqrt(4.812 +1.6632)=5.089 ft

average velocity of the tennis ball =displacement of the tennis ball /total time taken = 5.089ft/1.447s=3.517 ft/s

displacement of the golf ball vertically = 11ft - 8.66 ft = 2.34 ft

displacement of the golf ball horizontally = 0.950ft +0.713 ft =1.663 ft

displacement of the golf ball = sqrt(2.342 +1.6632)=2.871 ft

average velocity of the golf ball =displacement of the golf ball /total time taken = 2.871 ft/1.447s=1.984 ft/s

golf ball has largest instantaneous velocity at the end of this time period because it is still moving and the other two are at rest .(rock is at rest and tennis ball reached max height ....at max height velocity =0 )

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