A stone is to be thrown so as to cover a horizontal distance f 3m. If the velocity of the projectile is 7 m/s, find :
(a) the angle at which is must be thrown.
(b) the largest horizontal displacement that is possible speed of 7 m/s.

Explanation

(a) Range `R=(u^(2))/(g) sin 2 theta`
`rArr sin2theta=(gR)/(u^(2))=(9.8xx3)/((7)^(2))=0.6=sin37^(@)rArrtheta=18.5^(@)`
angle of projection may be `=90^(@)-theta=90^(@)-18.5^(@)=71.5^(@)`
(b) For largest horizontal displacement `theta=45^(@)` maximum range `R_("max")=(u^(2))/(g)+((7)^(2))/(9.8)=(49)/(98)xx10=5m`.