In one-dimensional motion with constant acceleration, an object’s velocity changes from $v_{\mathrm{i}}$ to $v_{\mathrm{f}}$ over a time interval $\Delta t$. Which expression gives the magnitude of the acceleration?

• A. $\left|\frac{v_{\mathrm{f}}+v_{\mathrm{i}}}{\Delta t}\right|$
• B. $\left|\frac{v_{\mathrm{f}}-v_{\mathrm{i}}}{\Delta t}\right|$
• C. $\left|\frac{\Delta t}{v_{\mathrm{f}}-v_{\mathrm{i}}}\right|$
• D. $\left|v_{\mathrm{f}}-v_{\mathrm{i}}\right|$

Answer: (B)