Question

Express each of the following speed in metres per second (1) 36km per hours (2) 72km per hours

Answer 1

Answer:

i) 36 km hr⁻¹ to m sec⁻¹.

= (36 × 1000) m ÷ (1 × 60 × 60) sec.

= 36000 m ÷ 3600 sec

= 10 m sec⁻¹. (Answer)

or

36 × (5/18)

= 10 m sec⁻¹. (Answer)

ii) 72 km hr⁻¹ to m sec⁻¹.

= (72 × 1000) m ÷ (1 × 60 × 60) sec.

= 72000 m ÷ 3600 sec

= 20 m sec⁻¹. (Answer)

or

72 × (5/18)

= 20 m sec⁻¹. (Answer)

Explanation:

1 km = 1000 m.

1 hour = 3600 or i.e 60 × 60 sec.

[∵ 1 hr = 60 sec. 1 min = 60 sec. So 1 hr or 60 min = 60 × 60 sec = 3600 sec.]

∴ x km hr⁻¹ = 1000x/ 3600 m sec⁻¹.    (Let x be a variable number.)

= 5x/18 m sec⁻¹.

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