Which is a stringed Instrument?

Step 1: Analyze the question The question asks which of the listed instruments is a stringed instrument, meaning it produces sound from vibrating strings.

Step 2: Explain the concept Musical instruments are classified by how they produce sound:

• Percussion instruments: sound comes from striking a membrane or solid surface (e.g., drum).
• Wind instruments: sound comes from vibrating air columns (e.g., flute, saxophone, trumpet).
• Stringed instruments: sound comes from vibrating strings (e.g., guitar, violin, harp).

Step 3: Classify each option

• A. Drum: percussion. A stretched membrane vibrates when struck.
• B. Flute: wind instrument. Air blown across the opening makes the air column vibrate.
• C. Piano: stringed instrument. Pressing a key makes a felt hammer strike stretched metal strings, which vibrate and produce sound. (It is also often called a keyboard instrument, but the sound source is the strings.)
• D. Saxophone: wind instrument. A vibrating reed makes the air column vibrate.
• E. Trumpet: brass wind instrument. The player's vibrating lips make the air column vibrate.

Step 4: Answer Only the piano produces its sound from vibrating strings, so the answer is C. piano.

Exam tip: Match the sound source to the family:

• Strings → piano, guitar, violin
• Air column → flute, saxophone, trumpet
• Struck membrane → drum

In physics, the frequency of a vibrating string depends on its length, tension and mass per unit length: f = (1/2L)√(T/μ). This is why piano strings differ in length and thickness for different notes.