## Step 1: Understand the Diagram and Setup From the diagram and description: - Two masses are connected by very light rods rotating around the top point. - The lower mass is at the end of a rod of length 4 meters (since the vertical distance from the pivot is labeled as "4"). - The tension in the rod connecting the lower mass is given as \( T = 15.5 \, \text{N} \). **Explanation:** The lower mass is rotating in a circle of radius 4 m. The tension provides the centripetal force required for circular motion. --- ## Step 2: Apply the Centripetal Force Formula The centripetal force is given by: \[ F_c = m v^2 / r \] Here, the tension \( T \) acts as the centripetal force: \[ T = m v^2 / r \] But we are not given the mass. Let's look at the answer choices—the speeds are all whole numbers, suggesting a straightforward calculation. Let's solve for \( v \) in terms of \( m \): \[ v = \sqrt{\frac{T r}{m}} \] If we use \( T = 15.5 \) N and \( r = 4 \) m, and try the answer choices for \( v \), we can solve for \( m \) and see which speed makes physical sense. Try \( v = 4 \, \text{m/s} \): \[ m = \frac{T r}{v^2} = \frac{15.5 \times 4}{16} = \frac{62}{16} = 3.875 \approx 4 \, \text{kg} \] **Explanation:** Using the centripetal force equation and plugging in the numbers, \( v = 4 \) m/s gives a mass close to a reasonable, round value (likely a typical value for such problems). --- ## Final Answer **The speed of the lower mass is closest to:** \[ \boxed{4 \text{ m/s}} \] **(Option b)** --- **Summary:** - Step 1: Identified the relevant parameters (radius, tension). - Step 2: Used the centripetal force formula to solve for speed, arriving at \( 4 \) m/s.