Question

An airplane flies with a constant speed of $800km\,h{{r}^{-1}}$. How long will it take to travel a distance of $2800km$?

Answer 1

Hint: The speed of the airplane is given. A speed only has magnitude and no direction. Speed depends on the distance travelled and the time taken. Substituting given values in the formula for speed, the time taken can be calculated. Convert the units as required.

Formula used:
$s=\dfrac{d}{t}$

Complete answer:
The speed is defined as the distance travelled in unit time. Its SI unit is $m{{s}^{-1}}$. It is given by-
$s=\dfrac{d}{t}$ ------- (1)
Here, $s$ is the speed
$d$ is the distance
$t$ is time taken
Given, an airplane is travelling at speed $800km\,h{{r}^{-1}}$. It travels a distance of $2800km$.
Substituting given values in eq (1), we can calculate the time taken to travel the given distance as
$\begin{align}
  & 800=\dfrac{2800}{t} \\
 & \Rightarrow t=\dfrac{2800}{80} \\
 & \therefore t=35\,hours \\
\end{align}$
The time taken by the airplane is $35\,hours$
Therefore, the time taken by the airplane to travel $2800km$ is $35\,hours$.

Additional Information:
According to Newton’s second law of motion, a force is required to move a body or change its state of rest or motion. When an object accelerates, an external force acts on it and the force depends on the mass and acceleration of the body on which it acts. According to Newton’s third law of motion, when a body exerts a force on another body, the other body exerts an equal and opposite force on this body.

Note:
Speed is a scalar quantity, i.e. it has only magnitude represented by its unit. $km\,h{{r}^{-1}}$ is the MKS unit of speed, which is a bigger unit than SI unit. The power from fuel is the force that propels the airplane forward. It is given a streamline shape to cut through the air.