Chapter 12, Problem 1FP

Initially, the car travels along a straight road with a speed of 35 m/s. If the brakes are applied and the speed of the car is reduced to 10 m/s in 15 s, determine the constant deceleration of the car.

To determine

The constant deceleration of the car.

Answer to Problem 1FP

The constant deceleration of the car is $1.6666{\text{m/s}}^2$.

Explanation of Solution

Given:

The initial velocity of the car is $v_0=35\text{m/s}$.

The final velocity of the car is $v=10\text{m/s}$ at the time of $t=15\text{s}$.

Write the formula for velocity of the car at constant acceleration.

$v=v_0+a_{c}t$ (1)

Here, $a_c$ is the constant acceleration.

Conclusion:

Substitute $35\text{m/s}$ for $v_0$, $10\text{m/s}$ for $v$ and $15\text{s}$ for $t$ in Equation (1).

$\begin{array}{l}10=35+a_c\left(15\right)\\ 10-35=15a_c\\ -25=15a_c\\ a_c=\frac{-25}{15}\end{array}$

$a_c=-1.6666{\text{m/s}}^2$

Here, the negative sign indicates the acceleration is in opposite direction that is deceleration.

Thus, the constant deceleration of the car is $1.6666{\text{m/s}}^2$.