Question

A man driving a car traveling at 20 m/sec slams on the brakes and decelerates at 3.25

Answer 1

Recall that

${v_f}^2-{v_i}^2=2a\Delta x$

where $v_i$ and $v_f$ are initial and final velocities, respectively; $a$ is acceleration; and $\Delta x$ is the net displacement, or distance if the object is moving in a single direction.

The car has initial speed 20 m/s and acceleration -3.25 m/s². It comes to a stop, so it has 0 final speed. Then

0² - (20 m/s)² = 2 (-3.25 m/s²) ∆x

∆x = (20 m/s)² / (7.5 m/s²) ≈ 53.3 m