Question #84914

1 Answer
Antoine
May 6, 2015

My attemp.

Assuming no resistive forces except gravity(that is the stone is in free fall)

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(1) the time to reach maximum height

Use the equation of motion #v=u+at#

at maximum height #v=0ms^-1# #u=19.8ms^-1#

since this is free fall the acceleration is due to gravity pulling down on the stone

So, #a=-g=-9.8ms^-2#

#=>0=19.8-9.8t=>t=19.8/9.8=2.02s#

(2) the maximum height(#H#)

Use #s=ut+1/2at^2#

#s=H#
#u=19.8ms^-1#
#a=-9.8ms^-2#
#t=2s#

#=>H=19.8(2)-(9.8xx(2)^2)/2=20m#

(3) Hum, i don't get what you're asking here,sorry

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