A stone is dropped from the peak of a hill. It covers a distance of 30m in last second of its motion. What is height of the peak?

1 Answer
Apr 15, 2017

Answer:

#"peak height : "62.16" "meters#

Explanation:

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#"let the arrival time of Object from A to B be t. "#

#AC=1/2 g t^2#

#AB=1/2 g (t-1)^2#

#AC-AB=30" "meters#

#30=1/2 g t^2-1/2 g(t-1)^2#

#30=1/2g[t^2-(t-1)^2]#

#(30*2)/g=t^2-(t^2-2t+1)#

#60/g=cancel(t^2)-cancel(t^2)+2t-1#

#60/g+1=2t#

#(60+g)/g=2t#

#2t=7.12#

#t=(7.12)/2#

#t=3.56 sec#

#"peak height="AC=1/2*g*t^2#

#AC=1/2*9.81*(3.56)^2#

#AC=62.16" "meters#