7. A can of spinach with mass of 0.14 kg loses 28 J of potential energy falling off of a shelf. How high was the can before it fell?

Here's how to solve this problem:<br /><br />1. **Understand the concept:** Potential energy (PE) is given by the formula PE = mgh, where m is the mass, g is the acceleration due to gravity (approximately 9.8 m/s² on Earth), and h is the height.<br /><br />2. **Rearrange the formula:** We want to find the height (h), so we rearrange the formula to h = PE / (mg)<br /><br />3. **Plug in the values:**<br /> * PE = 28 J<br /> * m = 0.14 kg<br /> * g = 9.8 m/s²<br /><br />4. **Calculate:** h = 28 J / (0.14 kg * 9.8 m/s²) = 20.4 meters (approximately)<br /><br />**Answer:** The can of spinach was approximately 20.4 meters high before it fell.<br />