Q25 of 43 Page 85

A particle projected from the ground move at 45° with horizontal one second after projection and speed is minimum two seconds after projection. The angle of projection of particle is (neglect air resistance)?

Let: u = Initial Velocity





At any instantaneous time t:


And


So, at any time t:


X – Axis:



…1


Also,


…2


Y – Axis:



…3


Also,


…4


Net speed at time t



So,




Now, it is given that at t = 2s, v is minimum


Now, is always constant. Thus v can be minimum only if = zero.


At t = 2 s


…5


Given: At t = 1 s




At t = 1 s


And also,


So, …6


Now, putting 5 in 6, we get:


...7


Now, dividing 5 by 7, we get:




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