Question

A ball is thrown with velocity 8 ms-1
making an angle 60° with the horizo-
ntal. Its velocity will be perpendi-
cular to the direction of initial
velocity of projection after a time of​

Answer 1

Answer:

let velocity of body after time t is perpendicular upon initial velocity .

velocity after time t

v = ucos∅ i + (usin∅ -gt ) j

initial velocity

v° = ucos∅ i + usin∅ j

because v and v° is perpendicular so,

v.v° = 0

{ucos∅ i + (usin∅ -gt) j }{ucos∅ i + usin∅ j } =0

u²cos²∅ +u²sin²∅ -usin∅.gt =0

u - sin∅gt = 0

t = u/sin∅g

=8/sin60.10

=8/√3/210

=1.6√3 sec

t = 1.6√3 sec

Explanation: