A stone is dropped from the top of a tower of height ‘H’ ,in last second of journey it travels a distance of 0.36 H. Then height H and time of fall of stone is g=10m/s2
see full answer
Your Exam Success, Personally Taken Care Of
1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.
An Intiative by Sri Chaitanya
a
2050m, 10s
b
125m, 5s
c
150m, 7s
d
500m, 20s
answer is B.
(Unlock A.I Detailed Solution for FREE)
Best Courses for You
JEE
NEET
Foundation JEE
Foundation NEET
CBSE
Detailed Solution
Let ‘n’ is last sec Sn is distance covered in last secwe know, S=Ut+12at2, here displacement=s=H; initial velocity=U=0; acceleration due to gravity=a=g; total time elapsed=t=n; substitute given values in the equation H=12gn2---(1) Distance travelled before the last second =H−0.36H=0.64Hdistance covered before last second=12gn−12=0.64H substitute equation (1) ⇒12gn−12=0.6412gn2 ⇒0.64n2=n−12 ⇒0.64n2=n−12⇒64100n2=n−12⇒8n=10n−10⇒2n=10⇒n=5⇒n=5=total time of flight The time of fall is 5sec h=12gn2 ⇒h=121052 ⇒h=2502 ⇒h=125m=height of tower