Final answer:
The weight of Robert's baseball card collection can be found by using the potential energy formula. By rearranging the formula and using the given potential energy value and height, the weight is calculated to be approximately 15 N.
Step-by-step explanation:
The question involves calculating the weight of Robert's baseball card collection based on its given potential energy (PE) and height above the ground. The formula to calculate potential energy is PE = mgh, where m is mass in kilograms, g is the acceleration due to gravity (usually 9.8 m/s2), and h is the height in meters. To find the weight (which is equal to the mass times the acceleration due to gravity, W = mg), we can rearrange the equation to m = PE / (gh).
Using the provided potential energy value of 30 J and height of 2 meters, we have m = 30 J / (9.8 m/s2 × 2 m). This calculation gives us a mass of approximately 1.53 kg. To find the weight, we multiply the mass by the acceleration due to gravity, W = 1.53 kg × 9.8 m/s2, resulting in a weight of approximately 15 N. Therefore, the correct answer is (b) 15 N.