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zhannawk [14.2K]
3 years ago
11

A man can row a boat at 4kmhr in still water. He rows the boat 2km upstream and 2 km back to his starting place in 2 hours. How

fast is the stream flowing
Physics
1 answer:
Softa [21]3 years ago
3 0

Answer:

2.83km/hr

Explanation:

Let stream flowing at the rat x km/hr

In still water

Speed of boat=4km/hr

Upstream speed=4-x

Downstream speed=4+x

Total time=2 hr

Time=Distance/speed

According to question

\frac{2}{4+x}+\frac{2}{4-x}=2

\frac{8-2x+8+2x}{(4+x)(4-x)}=2

\frac{16}{4^2-x^2}=2

Using the formula

(a+b)(a-b)=a^2-b^2

4^2-x^2=\frac{16}{2}

16-x^2=8

16-8=x^2

8=x^2

x=\sqrt{8}=2.83km/hr

Hence, the stream  is flowing at 2.83km/hr

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The electric field E of a charge is defined as E=F/Q where F is the Coulomb force and Q is the test charge. 

E=(1/Q)*k*(q*Q)/r², where k=9*10^9 N*m²/C², q is the point charge, Q is the test charge and r is the distance between the charges.

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