To find the velocity of an object moving with constant acceleration, we can use the following kinematic equation: \[ v = u + at \] Where: - \( v \) = final velocity (what we want to find) - \( u \) = initial velocity - \( a \) = acceleration - \( t \) = time ### Step-by-Step Solution 1. **Identify the given values**: - Initial velocity (\( u \)) = 5 m/s - Acceleration (\( a \)) = 2 m/s² - Time (\( t \)) = 4 seconds 2. **Substitute the values into the equation**: \[ v = 5 \, \text{m/s} + (2 \, \text{m/s}^2 \times 4 \, \text{s}) \] 3. **Calculate the acceleration component**: \[ 2 \, \text{m/s}^2 \times 4 \, \text{s} = 8 \, \text{m/s} \] 4. **Add this to the initial velocity**: \[ v = 5 \, \text{m/s} + 8 \, \text{m/s} = 13 \, \text{m/s} \] Thus, the final velocity after 4 seconds is **13 m/s**. ### Conclusion The correct option is **A. 13 m/s**. ### Explanation of Other Options - **B. 17 m/s**: This option is incorrect because it suggests an additional 4 m/s of velocity that does not come from the given acceleration over the specified time. - **C. 9 m/s**: This option is also incorrect. It implies a decrease in velocity, which contradicts the effect of positive acceleration acting on the object. - **D. 21 m/s**: This option is incorrect as it suggests an overestimation of the final velocity, likely due to a miscalculation of the acceleration component. ### Common Pitfalls - **Misunderstanding acceleration**: Remember that acceleration is the rate of change of velocity. If the acceleration is positive, the final velocity will always be greater than the initial velocity if time is positive. - **Forgetting to multiply acceleration by time**: Always ensure to multiply the acceleration by the time duration to find the total change in velocity. - **Confusing units**: Ensure that all units are consistent (e.g., m/s for velocity and m/s² for acceleration). ### Revision Summary - Use the formula \( v = u + at \) to find final velocity. - Substitute initial velocity, acceleration, and time correctly. - Calculate the change in velocity due to acceleration accurately. - Check your final answer against the options provided to ensure it matches.