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Answer for 1 8. a projectile is thrown horizontally from the top of a tower and strikes the ground after 3s at an angle of 45 with the horizontal. Find the height of the tower and speed with which the body was projected. Given g=9.8 ms-2

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A body is thrown horizontally from top of a tower and strikes the ground after three seconds at an angle 45∘ with horizontal. Find the height of the tower and initial speed of body.

(a)98.2m,12.2m/s(b)19.8m,14.6m/s(c)12.1m,19.2m/s(d)44.1m,29.4m/s

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A)

For the body thrown horizontally

ux=u

uy=0

ay=9.8

t=3

Therefore sy=uyt+12×9.8×32

=44.1m

[Let vv and vx be the vertical & horizotal component when it strikes the ground]

vy=uy+ayt

=0+9.8×3

=29.4m/s

The body strikes the ground at 45∘

tan45=vyvx=>29.4vx=1

Therefore vx=29.4

Therefore the horizontal speed at the time of projection is same as horizontal speed at the time of striking the ground

Therefore u=29.4

Hence d is the correct answer