**Two particles are projected in air with speed v0 at angles θ1 and θ2 (both acute) to the horizontal, respectively … (d)…**

###### Answers:

(a, b, c)

Key concept: When particle is thrown at an angle:

Time of flight. The total time taken by the projectile to go up and come down to the same level from which it was projected is called time of flight.

For vertical upward motion 0 = u sin θ – gt

⇒ t = (n sin θ /g)

Now as time taken to go up is equal to the time taken to come down, so

Time of flight T = 2t = 2usin θ/g

Time of flight can also be expressed as: T = 2.uy /g

(where n is the vertical component of initial velocity).

(ii) Horizontal range : It is the horizontal distance travelled by a body ’ during the time of flight.

So by using second equation of motion in x-direction.