Question

From the top of tower of height 100m, ball A is projected horizontally with a speed of 25m/s. Find its range and time taken ​

Answer 1

• Distance travelled=Height of tower=s=100m
• initial velocity=u=25m/s
• Acceleration due to gravity=g=10m/s^2
• Time=t

Using second equation of kinematics

$\boxed{\sf s=ut+\dfrac{1}{2}at^2}$

$\\ \sf\longmapsto 100=25t+\dfrac{1}{2}\times 10\times t^2$

$\\ \sf\longmapsto 100=25t+5t^2$

$\\ \sf\longmapsto 5t^2+25t-100=0$

Finding discrimant

$\\ \sf\longmapsto D=b^2-4ac$

$\\ \sf\longmapsto D=(25)^2-4(5)(100)$

$\\ \sf\longmapsto D=625-200$

$\\ \sf\longmapsto D=-1375\lt 0$

• It has imaginary roots