Which instrument measures the speed of rotation of a shaft? MCQ with Answer and Explanation

Which instrument measures the speed of rotation of a shaft?
A. Anemometer
B. Tachometer
C. Odometer
D. Speedometer
Answer: Option B
Solution (By JKExamLibrary)
Tachometer measures rotational speed (RPM). Speedometer vehicle speed. Odometer distance.

This question belongs to: Science Physics

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Practice More Physics Questions

Question #1 Report Error
The device that protects electrical circuits from overload is
A. Fuse
B. Capacitor
C. Resistor
D. Switch

Correct Answer: Option A


Explanation:
Fuse melts and breaks circuit when current exceeds rating. MCB (Miniature Circuit Breaker) does same but resettable. Switch only turns on/off. Resistor limits current but doesn't break.

This question belongs to: Science Physics
Question #2 Report Error
Escape velocity from a planet of mass M and radius R is v. For another planet of mass 4M and radius 2R, escape velocity is
A. √2 v
B. v
C. v/√2
D. 2v

Correct Answer: Option A


Explanation:
v_esc ∝ √(M/R). New ∝ √(4M/2R) = √(2M/R) = √2 √(M/R) = √2 v.

This question belongs to: Science Physics
Question #3 Report Error
When an ambulance with a blaring siren moves towards an observer, the pitch of the siren appears to be higher. This is due to:
A. Interference of sound waves
B. The Doppler Effect
C. Reverberation
D. Acoustic resonance

Correct Answer: Option B


Explanation:
The Doppler Effect is the apparent change in the frequency (and thus pitch) of a wave due to the relative motion between the source and the observer. As the ambulance approaches, sound waves get compressed, increasing the perceived frequency (higher pitch). As it moves away, waves stretch, lowering the frequency.

This question belongs to: Science Physics