Final answer:
When a penny slides into another stationary penny, it reflects 80% of the original energy.
Step-by-step explanation:
When a person slides a penny into another stationary penny, some of the original energy is lost. This loss of energy is due to friction between the two pennies and the surface they are sliding on. The amount of energy reflected, or retained by the sliding penny, can be calculated by comparing the final energy of the sliding penny to the initial energy.
Let's assume the initial energy of the sliding penny is 100 J. After the slide, the sliding penny has a final energy of 80 J. To find the percentage of energy reflected, we can use the formula:
Percentage of energy reflected = (Final energy / Initial energy) × 100%
Plugging in the values, we get:
Percentage of energy reflected = (80 J / 100 J) × 100% = 80%
Therefore, the answer is 80%.