Kai was 200 meters north of the library when he remembered he had to return some books to the library. It took him 200 seconds to do the round trip. Which best describes Kal's roundtrip? His speed was 1m/s and his velocity was His speed was 2m/s and his velocity was 0. His speed was 1m/s and his velocity was 1m/s north. His speed was 2m/s and his velocity was 2m/s south.

To solve this problem, let's analyze the situation step by step:<br /><br />### Step 1: Understanding the round trip<br />- Kai was **200 meters north** of the library.<br />- He traveled back to the library (200 meters south) and then returned to his starting point (200 meters north).<br />- The total distance covered during the round trip is:<br /> \[<br /> \text{Total Distance} = 200 \, \text{meters (to the library)} + 200 \, \text{meters (back to the starting point)} = 400 \, \text{meters}.<br /> \]<br /><br />- The **displacement** for the round trip is:<br /> \[<br /> \text{Displacement} = \text{Final Position} - \text{Initial Position}.<br /> \]<br /> Since he ended up at the same position where he started, the displacement is:<br /> \[<br /> \text{Displacement} = 0 \, \text{meters}.<br /> \]<br /><br />### Step 2: Calculating speed<br />Speed is defined as the total distance traveled divided by the time taken:<br />\[<br />\text{Speed} = \frac{\text{Total Distance}}{\text{Time Taken}}.<br />\]<br />The total distance is \( 400 \, \text{meters} \), and the time taken is \( 200 \, \text{seconds} \). Thus:<br />\[<br />\text{Speed} = \frac{400}{200} = 2 \, \text{m/s}.<br />\]<br /><br />### Step 3: Calculating velocity<br />Velocity is defined as the displacement divided by the time taken:<br />\[<br />\text{Velocity} = \frac{\text{Displacement}}{\text{Time Taken}}.<br />\]<br />The displacement is \( 0 \, \text{meters} \), and the time taken is \( 200 \, \text{seconds} \). Thus:<br />\[<br />\text{Velocity} = \frac{0}{200} = 0 \, \text{m/s}.<br />\]<br /><br />### Step 4: Choosing the correct option<br />From the calculations:<br />- Kai's **speed** is \( 2 \, \text{m/s} \).<br />- Kai's **velocity** is \( 0 \, \text{m/s} \).<br /><br />The correct answer is:<br />**"His speed was \( 2 \, \text{m/s} \) and his velocity was 0."**