GED Science TestPhysical ScienceHard
A student is observing a pendulum swinging back and forth. They notice that the pendulum eventually comes to a stop due to air resistance and friction at the pivot point. This observation demonstrates a real-world example of:
- AEnergy dissipation
- BConservation of momentum
- CConservation of mechanical energy
- DResonance
Show answer & explanationAnswer & explanation
Correct answer: A. Energy dissipation
While mechanical energy is conserved in an ideal pendulum, in a real-world scenario, non-conservative forces like air resistance and friction do work, converting mechanical energy into other forms (like heat and sound). This process is known as energy dissipation, where useful mechanical energy is 'lost' from the system.
Why the other options are wrong
- B. Conservation of momentum applies when no external forces act, but here, external resistive forces are present.
- C. Conservation of mechanical energy applies only in ideal systems without non-conservative forces like friction and air resistance. The pendulum stopping shows it's not conserved.
- D. Resonance is the phenomenon where an oscillating system is driven at its natural frequency, leading to large amplitude oscillations, which is not what 'coming to a stop' demonstrates.
Energy Dissipation
Energy dissipation is the process by which energy is transformed from more useful forms (like mechanical energy) into less useful or unusable forms (like heat or sound) due to non-conservative forces such as friction and air resistance.
- Reduces the total mechanical energy of a system.
- Always occurs in real-world physical systems.
- Often results in energy being converted to heat.
Memory trick: Real systems 'Dissipate' energy, like a fading echo.