Describe 4 everyday situations where mechanical energy is approximately conserved because work done by the non-conservative forces is ignorable. Please mention which non-conservative force is doing negligible work in each case you cite.
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Mechanical energy is approximately conserved in situations where there is negligible work done by non-conservative forces. Non-conservative forces are those forces that dissipate or remove energy from a system. Here are four everyday situations where mechanical energy is conserved, with the non-conservative force that does negligible work mentioned in each case:
1. Swinging on a playground swing: When you swing on a playground swing, the work done by air resistance is ignorable. Air resistance is the non-conservative force that opposes the motion of the swing, but its effect is typically small and can be neglected in most cases. Therefore, the mechanical energy of the swing, in the form of kinetic and potential energy, remains approximately conserved.
2. Roller coaster ride: On a roller coaster, the work done by friction is usually negligible. Friction acts between the coaster and the tracks, but the presence of wheels and careful design minimize its effect on the conservation of mechanical energy. Thus, the coaster's total mechanical energy, consisting of kinetic and gravitational potential energy, remains conserved during the ride.
3. Pendulum in motion: In the absence of air resistance, a pendulum swinging back and forth conserves its mechanical energy. In this case, the negligible work is done by air resistance, which has minimal impact on the motion of the pendulum.
4. Bouncing ball: Suppose you drop a ball on a hard surface and it bounces back up to its initial height. In this scenario, the work done by air resistance is considered negligible because the ball's motion is primarily influenced by gravity and the interaction with the ground. The mechanical energy of the ball, including its potential and kinetic energy, is approximately conserved during each bounce.
It's important to note that while these examples assume negligible work done by non-conservative forces, in reality, these forces are never completely absent. However, their impact on the conservation of mechanical energy is minimal and can be safely ignored in these everyday situations.