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sergij07 [2.7K]

2 years ago

9

Gretchen runs the first 4.0 km of a race at 5.0 m/s. Then a stiff wind comes up, so she runs the last 1.0 km at only 4.0 m/s.

1 answer:

KIM [24]2 years ago

7 0

Answer:

The velocity is $v = 4.76 \ m/s$

Explanation:

From the question we are told that

The first distance is $d_1 = 4.0 \ km = 4000 \ m$

The first speed is $v_1 = 5.0 \ m/s$

The second distance is $d_2 = 1.0 \ km = 1000 \ m$

The second speed is $v_2 = 4.0 \ m/s$

Generally the time taken for first distance is

$t_1 = \frac{d_1 }{v_1 }$

$t_1 = \frac{4000}{5}$

$t_1 = 800 \ s$

The time taken for second distance is

$t_1 = \frac{d_2 }{v_2 }$

$t_1 = \frac{1000}{4}$

$t_1 = 250 \ s$

The total time is mathematically represented as

$t = t_1 + t_2$

=> $t = 800 + 250$

=> $t = 1050 \ s$

Generally the constant velocity that would let her finish at the same time is mathematically represented as

$v = \frac{d_1 + d_2}{t }$

=> $v = \frac{4000 + 1000}{1050 }$

=> $v = 4.76 \ m/s$

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A toroidal solenoid has an inner radius of 12.0 cm and an outer radius of 15.0 cm . It carries a current of 1.50 A . Part A How

tensa zangetsu [6.8K]

Answer:

The number of turns is $N = 1750 \ turns$

Explanation:

From the question we are told that

The inner radius is $r_i = 12.0 \ cm = 0.12 \ m$

The outer radius is $r_o = 15.0 \ cm = 0.15 \ m$

The current it carries is $I = 1.50 \ A$

The magnetic field is $B = 3.75 mT = 3.75 *10^{-3} \ T$

The distance from the center is $d = 14.0 \ cm = 0.14 \ m$

Generally the number of turns is mathematically represented as

$N = \frac{2 * \pi * d * B}{ \mu_o * r_o }$

Generally $\mu_o$ is the permeability of free space with value

$\mu_o = 4\pi * 10^{-7} \ N/A^2$

So

$N = \frac{2 * 3.142 * 0.14 * 3.75 *10^{-3} }{ 4\pi * 10^{-7} * 0.15 }$

$N = 1750 \ turns$

5 0

2 years ago

A football player kicks a football downfield. The height of the football increases until it reaches a maximum height of 15 yards

Trava [24]

Answer:

kick 1 has travelled 15 + 15 = 30 yards before hitting the ground

so kick 2 travels 25 + 25 = 50 yards before hitting the ground

first kick reached 8 yards and 2nd kick reached 20 yards

Explanation:

1st kick travelled 15 yards to reach maximum height of 8 yards

so, it has travelled 15 + 15 = 30 yards before hitting the ground

2nd kick is given by the equation

y (x) = -0.032x(x - 50)

$Y = 1.6 X - 0.032x^2$

we know that maximum height occurs is given as

$x = -\frac{b}{2a}$

$y =- \frac{1.6}{2(-0.032)} = 25$

and maximum height is

$y = 1.6\times 25 - 0.032\times 25^2$

y = 20

so kick 2 travels 25 + 25 = 50 yards before hitting the ground

first kick reached 8 yards and 2nd kick reached 20 yards

8 0

2 years ago

Read 2 more answers

Energy conservation with conservative forces: Two identical balls are thrown directly upward, ball A at speed v and ball B at sp

MatroZZZ [7]

Answer:

E) True. Ball B will go four times as high as ball A because it had four times the initial kinetic energ

Explanation:

To answer the final statements, let's pose the solution of the exercise

Energy is conserved

Initial

Em₀ = K

Em₀ = ½ m v²

Final

Emf = U = mg h

Em₀ = emf

½ m v² = mgh

h = v² / 2g

For ball A

h_A = v² / 2g

For ball B

h_B = (2v)² / 2g

h_B = 4 (v² / 2g) = 4 h_A

Let's review the claims

A) False. The neck acceleration is zero, it has the value of the acceleration of gravity

B) False. Ball B goes higher

C) False has 4 times the gravitational potential energy than ball A

D) False. It goes 4 times higher

E) True.

6 0

2 years ago

Deep-sea divers often breathe a mixture of helium and oxygen to avoid getting the "bends" from breathing high-pressure nitrogen.

kvv77 [185]

Answer:

0.69444 m, 0.08152 m, 0.32407 m, 0.03804 m

Explanation:

v = Velocity of sound

f = Frequency

Length of vocal tract is given by

$L=\dfrac{v}{4f}$

At f = 270 Hz v = 750 m/s

$L=\dfrac{750}{4\times 270}\\\Rightarrow L=0.69444\ m$

At f = 2300 Hz v = 750 m/s

$L=\dfrac{750}{4\times 2300}\\\Rightarrow L=0.08152\ m$

At f = 270 Hz v = 350 m/s

$L=\dfrac{350}{4\times 270}\\\Rightarrow L=0.32407\ m$

At f = 2300 Hz v = 350 m/s

$L=\dfrac{350}{4\times 2300}\\\Rightarrow L=0.03804\ m$

3 0

2 years ago

Suppose that now you want to make a scale model of the solar system using the same ball bearing to represent the sun. How far fr

Dahasolnce [82]

Answer:

d = 0.645 m <em>(assuming a radius of the ball bearing of 3 mm)</em>

Explanation:

<u>The given information is:</u>

<em>The distance from the center of the sun to the center of the earth is 1.496x10¹¹m = $d_{e}$ </em>
<em>The radius of the sun is 6.96x10⁸m = $r_{s}$ </em>

<u>We need to assume a radius for the ball bearing, so suppose that the radius is 3 mm = $r_{b}$ </u>.

First, we need to find how many times the radius of the sun is bigger respect to the radius of the ball bearing, which is given by the following equation:

$\frac{r_{s}}{r_{b}} = \frac{6.96\cdot 10^{8}m}{3\cdot 10^{-3}m} = 2.32\cdot 10^{11}$

Now, we can calculate the distance from the center of the sun to the center of the sphere representing the earth, $d_{s}$ :

[tex] d_{s} = \frac{d_{e}}{r_{s}/r_{b}} = \frac{1.496 \cdot 10^{11} m}{2.32\cdot 10^{11}} = 0.645 m

I hope it helps you!

7 0

2 years ago