A projectile thrown from the ground level at an angle of alpha, is vertically displaced 35 meters within the last one second before landing.How many meters might it have raised ? (Assume ;g=10 N/kg,There is no drag)

1 Answer
Apr 25, 2016

Answer:

#80m#

Explanation:

As understood the problem.

Let #h# be the height from which the projectile starts its downward flight. Also let #t# be the time of downward flight. Let this point be origin.
As drag is to be ignored,
Kinematic equation is
#s=ut+1/2g t^2#, inserting given values
#h_t=1/2xx10 t^2=5t^2# .....(1)

Let us find distance of flight in time #t-1#
#h_(t-1)=5(t-1)^2# .....(2)

It is given that displacement in #t^(th)# second is 35 meters. Subtracting (2) from (1) and setting it equal to the given value.
#h_t-h_(t-1)=5t^2-5(t-1)^2=35#, Simplifying and solving for #t#

#5t^2-5(t^2-2t+1)=35#
or #(10t-5)=35#
#=>t=4s#

From (1)
#h_t=5xx4^2#
#=80m#