Question

An object covers 40 m in 5 sec and another 80 in 5 sec. What is average of the object

Answer 1

Given:

An object covers 40 m in first 5 seconds and another 80 m in the next 5 seconds.

To find:

Average speed of the object

Calculation:

Average Speed is defined as the ratio of of Total distance covered by the body to the total time taken to cover that specific magnitude of distance.

Average speed is a scalar quantity having only magnitude and no direction. This is because the quantity contains distance as one of its parameters which is itself a scalar quantity.

$\therefore \: \: v \: avg. = \dfrac{total \: distance}{total \: speed}$

$= > v \: avg. = \dfrac{40 + 80}{5 + 5}$

$= > v \: avg. = \dfrac{120}{10}$

$= > v \: avg. = 12 \: m {s}^{ - 1}$

So average speed is 12 m/s.

Answer 2

$\bf{\red{\underline{\underline{\large{Question:-}}}}}$

An object covers 40m in 5 sec and another 80m in 5 sec. What is average speed of the object?

$\rule{400}{4}$

$\bf{\red{\underline{\underline{\large{Formula:-}}}}}$

$\sf{\large{ Average \:speed\:=\:\frac{Total\:distance}{Total\:time}}}$

$\bf{\red{\underline{\underline{\large{Answer:-}}}}}$

$\sf{\pink{\underline{In \:first\: part\: of\: journey:-}}}$

$\sf{\: \: \bullet\: {d}_{1}\:=\:40m}$

$\sf{\: \: \bullet\: {t}_{1}\:=\:5sec}$

$\textsf{\pink{\underline{In second part of journey:-}}}$

$\sf{\: \: \bullet {d}_{2}\:=\:80m}$

$\sf{\: \: \bullet {t}_{2}\:=\:5sec}$

$\textsf{\pink{\underline{Finding average speed:-}}}$

$\sf{\bullet \blue{Total\:distance}\:=\:d\:={d}_{1}\:+\:{d}_{2}\:=\:40m}$

$\sf{+\:80m\: \blue{=\:120m}}$

$\sf{\bullet \blue{Total\:time}\:=\:t\:={t}_{1}\:+\:{t}_{2}\:=\:5sec\:+}$

$\sf{5sec\:\blue{=\:10sec}}$

$\sf{\bullet Average \:speed\:=\:\frac{Total\:distance}{Total\:time}}$

$\sf{\implies\: Average\:speed\:=\:\frac{d}{t}}$

$\sf{\implies\: Average\:speed\:=\:\frac{120m}{10sec}}$

$\sf{\implies\: Average \: speed\:=\:12m/s}$

$\large{\underline{\boxed{\green{\bf{Average\:speed\:=\:12m/s}}}}}$

$\bf{\red{\underline{\underline{\large{Additional\:information:-}}}}}$

• Since distance is a scalar quantity, so total distance is also a scalar quantity and hence average speed is also a scalar quantity
• Scalar quantity means that the quantity has only magnitude and unit
• A vector quantity means that the quantity has magnitude, unit and direction(shown by +ve or -ve sign)
• We can solve average speed by finding slope of a distance - time graph.