Question

A ball is projected with velocity 20 √3 m/s at an angle of 60° with the horizontal the time taken after which the velocity vector will make an angle of 30° with horizontal is??

Answer 1

Answer:

2 seconds

Explanation:

as initial vertical component will be 20√3 *Sin(60)=30m/s

    initial horizontal component (which will remain same throughout its          

    journey) will  be 20√3*Cos(60)=10√3 m/s

    now

    when velocity vector make an angle of 30 degrees with the hozontal    

    then also the horizontal component remains same as 10√3 m/s

    so, suppose the magnitude of velocity vector V be x m/s

    therefore  x*Cos(30)=10√3 m/s

    hence, magniutde of V is x=20m/s

    therefor vertical vector will be 20*Sin(30) =10m/s

    now according to equation "v=u=at"

    time taken to decrease its velocity fron 30 m/s to 10m/s(while moving upward) will be given by

    10=30+(-10)*t

    -10t=-20

     t=2s

   

     

Answer 2

Answer: 2 sec

Explanation: