Question

A particle is projected at angle 60º with speed 10√3 , from the point ' A ' as shown in the fig. At the same time the wedge is made to move with speed 10√3 towards right as shown in the figure. Then the time after which particle will strike with wedge is (g = 10 m/sec² ) :

(A) 2 sec 

(B) 2 √3 sec

(C) 4 / √3 sec 

(D) none of these

Answer 1

Correct option: (A) 2 sec

Explanation:

Suppose particle strikes wedge at height ‘S’ after time t. S = 15t - 1/2 10 t² = 15t – 5 t² . During this time distance travelled by particle in horizontal direction =  5 √3 t Also wedge has travelled travelled extra distance.

Total distance travelled by wedge in time t = 10 √3 t. = 5 √3 t + 3 (15 – 5t² ) ⇒ t = 2 sec.

Alternate Sol.

(by Relative Motion)