To determine the final velocity of an object moving in a straight line with an initial velocity and constant acceleration, we can use the following kinematic equation: \[ v = u + at \] Where: - \( v \) = final velocity (m/s) - \( u \) = initial velocity (m/s) - \( a \) = acceleration (m/s²) - \( t \) = time (s) ### Step-by-Step Explanation 1. **Identify the Given Values**: - Initial velocity (\( u \)) = 10 m/s - Acceleration (\( a \)) = 2 m/s² - Time (\( t \)) = 5 s 2. **Substitute the Values into the Equation**: We will substitute the known values into the kinematic equation: \[ v = 10 \, \text{m/s} + (2 \, \text{m/s}^2 \times 5 \, \text{s}) \] 3. **Calculate the Acceleration Component**: First, calculate the product of acceleration and time: \[ 2 \, \text{m/s}^2 \times 5 \, \text{s} = 10 \, \text{m/s} \] 4. **Add the Initial Velocity**: Now, add this result to the initial velocity: \[ v = 10 \, \text{m/s} + 10 \, \text{m/s} = 20 \, \text{m/s} \] 5. **Final Result**: Therefore, the final velocity after 5 seconds is: \[ v = 20 \, \text{m/s} \] ### Conclusion The correct answer is **B. 20 m/s**. ### Explanation of Other Options - **Option A (10 m/s)**: This option suggests that the object does not change its velocity, which is incorrect because the object is experiencing a constant acceleration of 2 m/s². Thus, the velocity must increase over time. - **Option C (30 m/s)**: This option incorrectly assumes a larger increase in velocity than what is calculated. The calculation shows that the increase in velocity due to acceleration over 5 seconds is exactly 10 m/s, leading to a final velocity of 20 m/s, not 30 m/s. - **Option D (40 m/s)**: This option suggests an even larger increase in velocity, which would imply an acceleration much greater than what is given. The correct calculation shows that the final velocity is only 20 m/s after 5 seconds, not 40 m/s. ### Common Pitfalls - **Ignoring the effect of acceleration**: Some students might forget to account for the acceleration when calculating the final velocity. - **Misunderstanding the formula**: Ensure that the correct kinematic equation is used and that all units are consistent (e.g., m/s for velocity and m/s² for acceleration). - **Calculation errors**: Double-check arithmetic operations, especially when multiplying acceleration by time. ### Revision Summary - Use the kinematic equation \( v = u + at \) to find final velocity. - Substitute known values carefully and perform calculations step-by-step. - Understand that acceleration changes the velocity over time. - Always verify your final answer against the context of the problem.