Question

A particle is projected from a horizontal floor with speed `10(m)/(s)` at an angle `30^@` with the floor and striking the floor after sometime. State which is correct.
A. Velocity of particle will be perpendicular to initial direction two seconds after projection.
B. Minimum speed of particle will be `5m//sec`.
C. Displecement of particle after half second will be `35//4m`.
D. None of these

Answer 1

Correct Answer - D
For `A`

Velocity of the particle will be particular to the initial direction when `10-gsin30^(@)t=0`
`:. T=2s`,
but total time of flight `=(2usin30^(@))/(g)=1s`.
So not possible
For `B`
Minimum speed during the motion is
`=u cos 30^(@)=10xx(sqrt(3))/(2)=5sqrt(3)m//s`
For `B`
`t=(1)/(2)` second
`:. `particle is at highest point.
Where, displacement `=sqrt((R^(2))/(4)+H^(2))=(5sqrt(3))/(4)m`