Question

felipe drives his car at a velocity of 28 m/s. he applies the brake, which slows the vehicle down at a rate of 6.4 m/s² and causes it to slow to a stop. how long does it take for the car to stop? round your answer to the nearest tenth.

Explanation:

Step1: Identify the kinematic - equation

We use the equation $v = v_0+at$, where $v$ is final velocity, $v_0$ is initial velocity, $a$ is acceleration and $t$ is time. The car stops, so $v = 0$, $v_0=28\ m/s$ and $a=- 6.4\ m/s^{2}$ (negative because it's deceleration).

Step2: Rearrange the equation for time

From $v = v_0+at$, we can solve for $t$: $t=\frac{v - v_0}{a}$.

Step3: Substitute the values

Substitute $v = 0$, $v_0 = 28\ m/s$ and $a=-6.4\ m/s^{2}$ into the formula: $t=\frac{0 - 28}{-6.4}=\frac{-28}{-6.4}=4.375\ s$.

Step4: Round the answer

Rounding $4.375\ s$ to the nearest tenth gives $4.4\ s$.

Answer:

$4.4$