NTA Abhyas JEE Main2020PhysicsMechanical Properties of SolidsPractice
The length of an elastic string is a m when the tension is 4 N , and ' b m when the tension is 5 N . The length in metre when the tension is 9 N , is
Options
- A4 a - 5 b
- B5 b - 4 a
- C9 b - 9 a
- Da + b
Correct answer
B. 5 b - 4 a
Step-by-step solution
T 1 = K l 1 - l T 2 = K ( l 2 - l ) So, T 1 T 2 = l 1 − l l 2 − l ∴     T 1 l 2 - T 1 l = T 2 l 1 - T 2 l T 2 - T 1 l = T 2 l 1 - T 1 l 2 l =   T 2 l 1 - T 1 l 2 ( T 2 - T 1 )   l = 5 a - 4 b .......(i) 5 - 4 = k ( b - a ) k = 1 b - a   ...(ii) 9 = k l ′                                                         ( l ′ = change