Question

9. Give examples to show that friction is both a friend and a foe.
10. Explain why objects moving in fluids must have special shapes.​

Answer 1

Answer:

friction is a friend

-->it helps us to walk comfortablely on the surface

-->helps to minimize the speed

friction is a foe

-->its causes wear and tear in objects

Objects moving in fluids face the friction of the fluid that opposes their motion. So Objects moving in fluids must have unique shapes called streamlined shapes to reduce the fluidfriction.

Answer 2

Explanation:

Answer:

Let the unknown number be x.

According to question,

\begin{gathered} \dashrightarrow \sf \frac{5}{12} \div x = \frac{ - 35}{18} \\ \\ \end{gathered}

⇢

12

5

÷x=

18

−35

\begin{gathered} \dashrightarrow \sf \frac{5}{12} \times \frac{1}{x} = \frac{ - 35}{18} \\ \\ \end{gathered}

⇢

12

5

×

x

1

=

18

−35

\begin{gathered}\dashrightarrow \sf \frac{5}{12x}= \frac{ - 35}{18} \\ \\ \end{gathered}

⇢

12x

5

=

18

−35

By Cross Multiplication :

\begin{gathered}\dashrightarrow \sf12x \times ( - 35) = 5\times 18 \\ \\ \end{gathered}

⇢