9: A post is being driven into the ground. The first strike drives the post 25 inches into the ground. Each additional strike dr
1 answer:
Answer:
99
Explanation:
First strike=25 in
Second strike=4/5*25=20 in
Third strike=4/5*20=16 in
Fourth strike=4/5*16=12.8 in
Fifth strike=4/5*12.8=10.24 in
sixth strike=4/5*10.24=8.192 in
seventh strike=4/5*8.192=6.5536 in
Total=(25+20+16+12.8+10.24+8.192+6.5536) in=98.7856 in
Taking this as a geometric series
where a is initial value taken as 25 for this case and r is rate taken as 4/5 or 0.8 in our case
To the nearest inches, sum is 99 in
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3) For the work-energy theorem, the work W done by the gravitational force on the rock is equal to the variation of kinetic energy of the rock, which is: