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lorasvet [3.4K]
3 years ago
8

Three swimmers who all swim at the same speed discuss how to cross a river in the shortest amount of time. Swimmer A will swim s

traight across the river at a right angle to the current. Swimmer B reasons that the current will carry A downstream, meaning that A will cover a greater distance to get across and therefore will take a longer time interval. B says he will aim at an upstream angle such that, allowing for the current, he will reach the other side directly across from where he starts, thus covering the shortest distance and arriving first. Swimmer C, reasoning that the time interval needed for B to cross will be longer than B expects because some of B’s effort will be spent battling the current, plans to aim at a downstream angle, so that the current assists rather than opposes him. This way he will be traveling at the highest speed and get across first. Which swimmer gets across first?
Physics
1 answer:
AleksAgata [21]3 years ago
5 0

Answer:

Swimmer A

Explanation:

The time required for a swimmer to cross a river is equal to the width of the river which is divided by the magnitude of the component of the velocity which is parallel to the width of the river.

In the given context, all the three swimmers A, B and C swims in a different angle relative to the direction of the flow of river. The swimmer A swims straight at a direction perpendicular to the direction of current of the river across the width of the river, so A will have the largest velocity component which is parallel to the width of the river. So the time taken by swimmer A will be the least to cross the river.

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dalvyx [7]

Answer:

(a) W_c=127.008 J

(b) W_g=148.176 J

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(d) v=3.4293m.s^{-1}

Explanation:

Given:

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  • constant downward acceleration, a_d= \frac{g}{7}

\Rightarrow That a constant upward acceleration of \frac{6g}{7} is applied in the presence of gravity.

∴a=- \frac{6g}{7}

  • height through which the block falls, d = 4.2 m

(a)

Force by the cord on the block,

F_c= M\times a

F_c=3.6\times (-6)\times\frac{9.8}{7}

F_c=-30.24 N

∴Work by the cord on the block,

W_c= F_c\times d

W_c= -30.24\times 4.2

We take -ve sign because the direction of force and the displacement are opposite to each other.

W_c=-127.008 J

(b)

Force on the block due to gravity:

F_g= M.g

∵the gravity is naturally a constant and we cannot change it

F_g=3.6\times 9.8

F_g=35.28 N

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W_g=F_g\times d

W_g=35.28\times 4.2

W_g=148.176 J

(c)

Kinetic energy of the block will be equal to the net work done i.e. sum of the two works.

mathematically:

K.E.= W_g+W_c

K.E.=148.176-127.008

K.E. = 21.168 J

(d)

From the equation of motion:

v^2=u^2+2a_d\times d

putting the respective values:

v=\sqrt{0^2+2\times \frac{9.8}{7}\times 4.2 }

v=3.4293m.s^{-1} is the speed when the block has fallen 4.2 meters.

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Answer:

D) equal to the flux of electric field through the Gaussian surface B.

Explanation:

Flux through S(A) = Flux through S (B ) =  Charge inside/ ∈₀

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What scientific question does Isaac Asimov most clearly address with his
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Answer:  C. can robots be trained to follow a moral code?

Explanation:

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Why is an object's density expressed as a relationship between two units?
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Probably for kind of the same reason that speed is expressed as a
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defon

The force of the racket affects the ball's motion because it changes the momentum of the ball.

<h3>Impulse received by the ball</h3>

The impulse received by the ball through the racket affects the motion because it changes the momentum of the ball.

The ball which is initially at rest, will gain momentum after been hit with the racket.

J = ΔP = Ft

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Learn more about impulse here: brainly.com/question/25700778

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