Resonance (amplification at natural frequency) is exploited in musical instruments (e.g., guitar body resonates with string frequencies) and tuning forks (designed to vibrate at precise frequency for calibration). Memory tip: 'Resonance applications: musical instruments (amplify sound), tuning forks (frequency standard), bridges (avoid resonance to prevent collapse)'. This application question tests wave phenomena uses, frequently appearing in competitive exams. Always link physical principles to practical applications; competitive exams emphasize real-world relevance of physics concepts, including both beneficial and hazardous aspects of resonance.
A block of mass 10 kg is accelerating at 2 m/s^2 on a horizontal surface under an applied force of 50 N. What is the magnitude of the frictional force opposing its motion?
Explanation:
According to Newton's Second Law, the net force on the block is F_net = mass * acceleration = 10 kg * 2 m/s^2 = 20 N. The net force is the difference between the applied forward force and the opposing frictional force (F_net = F_applied - F_friction). So, 20 N = 50 N - F_friction. Solving for friction gives F_friction = 50 - 20 = 30 N.
Explanation:
First law of thermodynamics: Energy is conserved in an isolated system. It changes forms (kinetic to potential etc.) but total constant. Perpetual motion machine impossible.
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