A student drops his textbook out of a window in a tall building. How high above the ground is the book when it is falling at a speed of 438 cm/s?
2 Answers
Feb 17, 2018
It is presumed that the given falling speed of book just is as it hits the ground.
Explanation:
Applicable kinematic expression is
#v^2-u^2=2gh#
Inserting given values in SI units we get
#(4.38)^2-(0)^2=2xx9.81xxh#
#=>h=(4.38)^2/(2xx9.81)=97.7\ cm#
Height given in
Feb 24, 2018
Alternate solution.
Explanation:
Let height of the window be
Let the book be at a height
Let the student drop the book with initial velocity
For free fall under gravity applicable kinematic expression is
#v^2-u^2=2gs#
Inserting given values in SI units we get
#(4.38)^2-(0)^2=2xx9.81xx(h-h_1)#
#=>(h-h_1)=(4.38)^2/(2xx9.81)#
#=>(h-h_1)=0.98#
#=>h_1=0.98-h\ m#