Concepts Of Physics MCQ Edition [Volume 1]PhysicsWave Motion and Waves on a String
A 4.0 kg block is suspended from the ceiling of an elevator by a string with a linear mass density of 19.2 10⁻³ kg m ⁻¹ . Determine the speed (relative to the string) at which a wave pulse can travel along the string, given that the elevator accelerates upward at a rate of 2.0 m s ⁻² . Use g = 10 m s ⁻² .
Options
- A41 m s ⁻¹
- B20 m s ⁻¹
- C50 m s ⁻¹
- D46 m s ⁻¹
Correct answer
C. 50 m s ⁻¹
Step-by-step solution
The effective acceleration of the block in the elevator accelerating upward is given by: g_ eff = g + a = 10 + 2.0 = 12.0 m s ⁻² The tension in the string is equal to the apparent weight of the suspended block: T = M g_ eff = 4.0 12.0 = 48 N The speed of a transverse wave pulse on a string is given by the formula: v = T Substituting the given values: v = 48 19.2 10⁻³ v = 48000 19.2 = 2500 v = 50 m s ⁻¹