Question

Um caminhão viaja pela estrada com velocidade de 70km/h. Diante de um obstáculo ele é freado e para cerca de 360 segundos depois. Qual foi a aceleração media?

Answer 1

Answer: $-0.054 m/s^{2}$

Explanation:

The question in english is written below:

A truck travels along the road at a speed of 70 km/h. It encounters an obstacle and brakes for about 360 seconds until it stops. What is the average acceleration of the truck?

Average acceleration $a_{ave}$ is the variation of velocity $\Delta V$ over a specified period of time $\Delta t$:

$a_{ave}=\frac{\Delta V}{\Delta t}}$

Where:

$\Delta V=V_{f}-V_{o}$

$V_{o}=70 \frac{km}{h}\frac{1000 m}{1 km} \frac{1 h}{3600 s}=19.44 m/s$ is the initial velocity

$V_{f}=0 m/s$ the final velocity

$\Delta t=360 s$

Then:

$a_{ave}=\frac{V_{f}-V_{o}}{\Delta t}}$

$a_{ave}=\frac{0 m/s-19.44 m/s}{360 s}}$

Finally:

$a_{ave}=-0.054 m/s^{2}$ Note the negative sign in the acceleration indicates the truck was decreasing its velocity until it stopped.