To find the final velocity of an object that is moving in a straight line with an initial velocity and constant acceleration, we can use the following kinematic equation: \[ v_f = v_i + a \cdot t \] Where: - \( v_f \) = final velocity - \( v_i \) = initial velocity - \( a \) = acceleration - \( t \) = time ### Step-by-Step Explanation 1. **Identify the Given Values**: - Initial velocity (\( v_i \)): 10 m/s - Acceleration (\( a \)): 2 m/s² - Time (\( t \)): 5 seconds 2. **Substitute the Values into the Formula**: We will substitute the known values into the kinematic equation: \[ v_f = 10 \, \text{m/s} + (2 \, \text{m/s}^2 \cdot 5 \, \text{s}) \] 3. **Calculate the Acceleration Component**: First, calculate the product of acceleration and time: \[ 2 \, \text{m/s}^2 \cdot 5 \, \text{s} = 10 \, \text{m/s} \] 4. **Add the Initial Velocity**: Now, add this result to the initial velocity: \[ v_f = 10 \, \text{m/s} + 10 \, \text{m/s} = 20 \, \text{m/s} \] 5. **Final Result**: Therefore, the final velocity (\( v_f \)) of the object after 5 seconds is: \[ v_f = 20 \, \text{m/s} \] ### Conclusion The correct answer is **B. 20 m/s**. ### Explanation of Other Options - **Option A: 10 m/s**: This option suggests that the final velocity is the same as the initial velocity. This is incorrect because the object is accelerating, which means its velocity is changing over time. - **Option C: 30 m/s**: This option is incorrect because it does not account for the correct calculation of the acceleration over the time period. The final velocity is not simply the initial velocity plus an arbitrary number. - **Option D: 40 m/s**: This option is also incorrect. It suggests an overestimation of the final velocity, likely due to misunderstanding the relationship between acceleration, time, and initial velocity. ### Common Pitfalls - **Forgetting to multiply acceleration by time**: A common mistake is to add the acceleration directly to the initial velocity without considering the time factor. - **Misunderstanding acceleration**: Remember that acceleration is the rate of change of velocity, and it must be applied over the time period to find the change in velocity. ### Revision Summary - Use the kinematic equation \( v_f = v_i + a \cdot t \) to find final velocity. - Substitute known values carefully and perform calculations step-by-step. - Ensure to multiply acceleration by time to find the total change in velocity. - Always check if the final answer makes sense in the context of the problem.