A projectile is fired with a speed u at an angle θ with the horizontal. Its speed when its direction of motion makes an angle α with the horizontal is?

A: usecθsecα
B: usecθsinα
C: ucosθsecα
D: usinθsecα
PLEASE EXPLAIN EACH AND EVERY STEP

1 Answer
Aug 7, 2017

Let the velocity of projection of the object be u with angle of projection θ with the horizontal direction.
The vertical component of the velocity of projection is usinθ and the horizontal component is ucosθ

Now if t be the time after the projection of the projectile, its direction of velocity makes angle α with the horizontal.Let the velocity of the projectile after t sec be v

The vertical component of the velocity after time t will be vsinα

But the horizontal component remains unaltered as ucosθ

So vcosα=ucosθ

v=1cosα×ucosθ=ucosθsecα

So option C is accepted