A block has a mass of 7 kg and on a surface with mhu= .7. Explain with forces, and prove mathematically, how the three situations could occur. A. The block is speeding up B. The block is slowing down C. The block is moving at a constant speed

Respuesta :

ANSWER:

A. F > 48.02 N

B. F < 48.02 N

C. F = 48.02 N

STEP-BY-STEP EXPLANATION:

Given:

Mass (m) = 7 kg

µ = 0.7

Balancing horizontal forces:

[tex]\begin{gathered} F=\mu N+ma\rightarrow F=\mu\cdot m\cdot g+ma \\ \text{ We replacing} \\ F=0.7\cdot7\cdot9.8+7a \\ F=48.02+7a \\ a=\frac{F-48.02}{7} \end{gathered}[/tex]

A. The block is speeding up

It means the block is having a positive value of acceleration:

[tex]\begin{gathered} a>0 \\ \frac{F-48.02}{7}>0 \\ F>48.02\text{ N} \end{gathered}[/tex]

B. The block is slowing down

[tex]\begin{gathered} a<0 \\ \frac{F-48.02}{7}<0 \\ F<48.02\text{ N} \end{gathered}[/tex]

C. The block is moving at a constant speed

[tex]\begin{gathered} a=0 \\ \frac{F-48.02}{7}=0 \\ F=48.02\text{ N} \end{gathered}[/tex]