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3 years ago

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

Physics

1 answer:

LekaFEV [45]3 years ago

8 0

The time taken to complete her run is 1.9 hr.

Explanation:

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:

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Explanation:

Given that rotational kinetic energy = $4.66*10^9J$

Mass of the fly wheel (m) = 19.7 kg

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$\omega = \sqrt{\frac{2(K.E)_{rt}}{I} }$

$\omega = \sqrt{\frac{2(KE)_{rt}}{1/2 mr^2} }$

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The answer is B. 7.

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A man does 500 J of work pushing a car a distance of 2 m. How much force does he apply? Assume there is no friction.

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The correct answer is A. 250N

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That is, work done=force×distance

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lions [1.4K]

Answer:

$vf_{1} =\frac{1}{3} v$ :Final block velocity (toward the left)

$vf_{2} =\frac{2}{3} v$ :Final mass velocity (to the right)

Explanation:

To solve this problem we apply the theory of shocks:

In an elastic shock the kinetic energy and the amount of linear movement or momentum are conserved.

Because the shock is elastic, the coefficient of elastic restitution (e) is equal to 1.

Principle of conservation of the momentum:

m1vi1+m2vi2=m1vf1+m2vf2 Equation 1

Formula to calculate the coefficient of elastic restitution (e):

$e=\frac{vf_{2}-vf_{1} }{vi_{1}-vi_{2} }$ Equation 2

m1: Block mass

m2: mass of the body that collides with the block

Vi1,vf1: initial, final velocity of the block

Vi2,vf2: initial, final velocity of the body that collides with the block

Of the problem data we know that:

m1=m , m2 = 2m, vi1=v and vi2=0, then, we replace this information in equation (1) :

mv+0=mvf1+2mvf2 we divide by m:

v=vf1+2vf2 Equation (3)

Because the shock is elastic, the coefficient of elastic restitution (e) is equal to 1,then , we we replace this information in equation (2)

$1=\frac{vf_{2}-vf_{1} }{v-0}$

v=vf2-vf1 Equation (4)

vf2=v+vf1 Equation (5)

We replace the equation 5 in the equation (3)

v=vf1+2(v+vf1)

v=vf1+2v+2vf1

-3vf1=v

$vf_{1} = -\frac{1}{3} v$

We replace Vf1=(-1/3)v in the equation (5):

$vf_{2} =v-\frac{1}{3} v$

$vf_{2} =\frac{2}{3} v$

Answer;

$vf_{1} =\frac{1}{3} v$ :Final block velocity (toward the left)

$vf_{2} =\frac{2}{3} v$ :Final mass velocity (to the right)

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