Question

A particle is projected upwards with a velocity of 100m/s at an angle of 60°with the vertical. Find the time when the particle will move perpendicular to its initial direction,taking g=10m/s2​

Answer 1

Explanation:

u=100sin60

0

i

^

+100cos60

0

j

^

=50

j

^

+50

3

i

^

v

=

u

−gt

j

^

=50

j

^

+50

3

i

^

−10t

j

^

=50

3

i

^

+(50−10t)

j

^

When velocity is perpendicular to initial velocity,

v

.

u

=0, or (50

3

i

^

+(50−10t)

j

^

).(50

j

^

+50

3

i

^

)=0 or, 7500+2500−500t=0

which gives, t=20s

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