Question

OK
PIW
3. A car travels 20 km in 20 minute. Find the speed
of car (a) kmh-1 (b) ms-1
[(a) 60 kmh-1 (b) 16.67 ms-11
i need 16 . 67 in detail ​

Answer 1

Explanation:

As per the provided information in the given question, we have :

• Distance travelled = 20 km
• Time taken (t) = 20 minutes

We are asked to calculate the speed of car in,

• km/h

• m/s

★ Calculating speed in km/h :

In order to find the speed of the car in km/h, we need to find the distance in km and time in hour first. After that, by applying the formula we'll calculate its speed in km/h.

⇒ Distance = 20 km [Already given in km]

⇒ Time = 20 minutes = $\sf { \dfrac{1}{3} }$ hr

We know that,

➝ 60 minutes = 1 hr

➝ 1 minute = $\sf { \dfrac{1}{60} }$ hr

➝ 20 minutes = $\sf { \dfrac{20}{60} }$ hr

➝ 20 minutes = $\sf { \dfrac{1}{3} }$ hr

Nlw, we know that,

$\\ \longrightarrow \quad \pmb{\boxed{\sf {Speed = \dfrac{Distance}{Time} }} }$

Substituting values,

$\\ \longrightarrow \sf{\quad {Speed_{(in \; kmh^{-1} )}= \dfrac{20}{\cfrac{1}{3} } \;kmh^{-1} }}$

$\\ \longrightarrow \sf{ \quad { Speed_{(in \; kmh^{-1} )} = 20 \times \dfrac{3}{1} \; kmh^{-1} }}$

$\\ \longrightarrow \bf{\quad \underline{ Speed_{(in \; kmh^{-1} )} = 60 \; kmh^{-1} }}$

Therefore, speed of the body in km/h is 60 km/h.

★ Calculating speed in m/s :

In order to find the speed of the car in m/s, we need to find the distance in m and time in seconds first. After that, by applying the formula we'll calculate its speed in m/s.

$\\ \longrightarrow \sf{\quad { Distance = 20 \; km}}$

• 1 km = 1000 m

$\\ \longrightarrow \sf{\quad { Distance = (20 \times 1000) \; m}}$

$\\ \longrightarrow \sf{\quad { Distance = 20000 \; m }}$

Now, Converting time into seconds.

$\\ \longrightarrow \sf{\quad { Time = 20 \; minutes}}$

• 1 minute = 60 seconds

$\\ \longrightarrow \sf{\quad { Time =( 20 \times 60) \; seconds}}$

$\\ \longrightarrow \sf{\quad { Time = 1200 \; seconds}}$

Formula to calculate speed,

$\\ \longrightarrow \quad \pmb{\boxed{\sf {Speed = \dfrac{Distance}{Time} }} }$

Substituting the values of distance & time in metre and seconds.

$\\ \longrightarrow \sf{\quad { Speed_{(in \; ms^{-1})} = \dfrac{2000}{1200} \; ms^{-1} }}$

$\\ \longrightarrow \sf{\quad { Speed_{(in \; ms^{-1})} = \dfrac{20000}{1200} \; ms^{-1} }}$

$\\ \longrightarrow \sf{\quad { Speed_{(in \; ms^{-1})} = \dfrac{200}{12} \; ms^{-1} }}$

$\\ \longrightarrow \sf{\quad { Speed_{(in \; ms^{-1})} = \dfrac{100}{6} \; ms^{-1} }}$

$\\ \longrightarrow \sf{\quad { Speed_{(in \; ms^{-1})} = \dfrac{50}{3} \; ms^{-1} }}$

$\\ \longrightarrow \bf{\quad \underline{ Speed_{(in \; ms^{-1} )} = 16.67 \; ms^{-1} }}$

Therefore, speed in m/s is 16.67 m/s.