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3 years ago

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A jogger runs 6 km north ,5 km east then another 4km north her average speed 8 km how long will it take her to complete her run

1 answer:

LekaFEV [45]3 years ago

8 0

The time taken to complete her run is 1.9 hr.

<u>Explanation:</u>

Speed is a scalar quantity and it is defined as the ratio of distance covered to the time taken to cover that distance. As distance is also a scalar quantity, so the directions given in the problem can be ignored. Thus, the distance covered by the jogger is the sum of kilometers given in problem.

Distance covered = 6+5+4 = 15 km

And the speed is given as 8 km/hr.

So the time taken will be ratio of distance to speed.

$\text { time }=\frac{\text {distance}}{\text {speed}}=\frac{15}{8}=1.9 \text { hour }$

So the jogger will take 1.9 hr to complete her run.

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Answer:

a) $r_1=1.36R$

b) $r_2=2.083R$

Explanation:

<u>Given:</u>

a) when the initial velocity of the projectile is 0.520 times the escape velocity from the earth.

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Now using conservation of Energy at earths surface and at distance r we have

$\dfrac{-GMm}{R}+\dfrac{m(0.52V_e)^2}{2}=\dfrac{-GMm}{r_1}\\\dfrac{-GMm}{R}+\dfrac{m\times 0.52^2\times \dfrac{2GM}{R}}{2}=\dfrac{-GMm}{r_1}\\r_2=1.36\ R$

b) when the Initial kinetic Energy of the projectile is 0.52 times the Kinetic Energy required to escape the Earth

Conservation of Energy we have

$\dfrac{-GMm}{R}+0.52\times KE_{escape}=\dfrac{-GMm}{r_2}\\\dfrac{-GMm}{R}+0.52\times\dfrac{m\times \dfrac{2GM}{R}}{2}=\dfrac{-GMm}{r_2}\\r_2=2.083\ R$

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How far will a bird have traveled in 13 seconds if it maintains a speed of 31 m/s

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