NTA Abhyas JEE Main2020PhysicsWaves and SoundPractice
A motorcycle starts from rest and accelerates along a straight path at 2 m s - 2 . At the starting point, there was a siren which produced sound at a constant frequency. How far has the motorcycle gone from the starting point, If now the rider hears the frequency of the siren at 94 % of its value as compared to when the motorcycle was rest? (Speed = 330 m s - 1 )
Options
- A49   m
- B98   m
- C147   m
- D196   m
Correct answer
B. 98   m
Step-by-step solution
For Motorcycle, u = 0 , a = 2   m   s - 2 Observe is in motion and source is at rest ⟹         n ′ = n v - v 2 v + v s ⟹ 94 100 n = n 330 - v o 330 ⟹ 330 - v o = 330 × 94 100 ⟹ v o = 330 - 94 × 33 10 = 33 × 6 10   m   s - 1 s = v 2 - u 2 2 a = 9 × 33 × 33 100 = 9 × 1089 100 = 98   m .