Convert the following (a) 20 m s⁻¹ into km h⁻¹. (b) 3 x 10⁸ m s⁻¹ into km h⁻¹ (c) 220 km h⁻¹ into m s⁻¹ 

Ans. [(a) 72 kmh. (b) 1.08 x 10¹⁰ km h⁻¹ (c) 61 m s⁻¹]



We know:

1 km = 1000 m
1 hr = 3600 s

To convert km (big unit) to m (small unit) we Multiply 1000 

Solution:

(a) 20 m s⁻¹ into km h⁻¹. 

To convert metre m (small unit) into kilometre km (big unit) we divide by 1000. Similarly, we divide by 3600 in converting second into hours. 

Thus

20 m s⁻¹    = `\frac {20/1000 }{1/3600}`   km h⁻¹

                = `\frac {20ｘ3600}{1000}`   km h⁻¹

                = 72 km h⁻¹ -----Ans.


(b) 3 x 10⁸ m s⁻¹ into km h⁻¹ 

3 x 10⁸ m s⁻¹ = `\frac {{3 x 10⁸}/1000 }{1/3600}`   km h⁻¹

                    = `\frac {3 x 10⁸ｘ3600}{1000}`   km h⁻¹

                    = 1.08 x 10¹⁰  km h⁻¹ -----Ans.


(c) 220 km h⁻¹ into m s⁻¹ 

To convert kilometre km (big unit) into metre m (small unit) we multiply 1000. Similarly, we multiply by 3600 in converting hours into seconds. 


220 km h⁻¹ = `\frac {220 x 1000 }{3600}`   m s⁻¹

                 = 61.1 m s⁻¹ -----Ans.


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