contestada

this is a 2 part question28) A 1100-kg car coasts on a horizontal road with a speed of 19 m/s. After crossing anunpaved, sandy stretch of road 32 m long, its speed decreases to 12 m/s. (a) Was the net work done on the car positive, negative, or zero? Explain. (b) Find the magnitude of the average net force on the car in the sandy section.

Respuesta :

ANSWER:

(a) negative

(b) -120.3 N

STEP-BY-STEP EXPLANATION:

(a)

The net work done on the car is negative because its speed decreases from 19 m/s to 12 m/s

(b)

The acceleration is found from the equationof motion that:

[tex]v^2-u^2=2\cdot a\cdot s[/tex]

Replacing and solving for a:

[tex]\begin{gathered} 12-19=2\cdot a\cdot32 \\ -7=64a \\ a=-\frac{7}{64}\frac{m}{s^2} \end{gathered}[/tex]

Therefore, the force would be:

[tex]\begin{gathered} F=m\cdot a \\ F=1100\cdot-\frac{7}{64} \\ F=-120.3\text{ N} \end{gathered}[/tex]