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2 years ago

Alex swims at an average speed of 45 m/min.how far does he swim in 1min 24 sec?

Physics

1 answer:

Drupady [299]2 years ago

8 0

Answer: 72m/1 min and 24 secs

Explanation:

He swims .75m/sec. im pretty sure i got it but let me know and ill help you out if its wrong

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A ray diagram for a refracted light ray is shown.

Rina8888 [55]

The dashed line represents the<u> normal </u>to the boundary

Explanation:

Refraction is a phenomenon that occurs when a ray of light crosses the interface between two mediums.

When this occurs, the ray of light changes direction and speed.

The new direction of the ray of light is given by Snell's law:

$n_1 sin \theta_1 = n_2 sin \theta_2$

where

$n_1$ is the index of refraction of the 1st medium

$n_2$ is the index of refraction of thre 2nd medium

$\theta_1$ is the angle of incidence, which is the angle between the direction of the incident ray and the normal to the boundary

$\theta_2$ is the angle of refraction, which is the angle between the direction of the refracted ray and the normal to the boundary

The index of refraction of a medium is the ratio between the speed of light in a vacuum (c) and the speed of light in that medium (v):

$n=\frac{c}{v}$

The figure in the question is missing, however you can find it in attachment.

We see that the dashed line is perpendicualr to the boundary between the two mediums, so it represents the normal.

So, the correct answer is

Normal

We note that in this case the ray of light bends towards the normal, this means that $\theta_2$ , therefore the second medium has a larger index of refraction ( $n_2>n_1$ ).

Learn more about refraction:

brainly.com/question/3183125

brainly.com/question/12370040

#LearnwithBrainly

7 0

3 years ago

Lightsail-2 is a spacecraft launched in June 2019 by the Planetary Society driven by radiation pressure on a solar sail of area

lozanna [386]

Answer:

$2.655\times 10^{13}\ photons$

Explanation:

Area of the solar sail = A = 30 m2

Solar constant = I = 1388 W/m2

Planck's constant = h = 6.626 × 10⁻³⁴ m²kg/s

Speed of light = c = 3×10⁸ m/s

Wavelength of light = $\lambda$ = 570 nm

Pressure from radiation

$P=2\frac{I}{c}\\\Rightarrow P=2\frac{1388}{3\times 10^8}\\\Rightarrow P=9.253\times 10^{-6}\ W$

Energy of a photon

$E=\frac{hc}{\lambda}\\\Rightarrow E=\frac{6.626\times 10^{-34}\times 3\times 10^8}{570\times 10^{-9}}\\\Rightarrow E=3.487\times 10^{-19}\ J$

Number of photons

$n=\frac{P}{E}\\\Rightarrow n=\frac{9.253\times 10^{-6}}{3.487\times 10^{-19}}\\\Rightarrow n=2.655\times 10^{13}\ photons$

Number of photons is $2.655\times 10^{13}\ photons$

3 0

3 years ago

1) A net force of 75.5 N is applied horizontally to slide a 225 kg crate across the floor.

dimulka [17.4K]

Answer:

The acceleration of the crate is $0.3356\,\frac{m}{s^2}$

Explanation:

Recall the formula that relates force,mass and acceleration from newton's second law;

$F=m\,a$

Then in our case, we know the force applied and we know the mass of the crate, so we can solve for the acceleration as shown below:

$F=m\,a\\75.5\,N=225\,\,kg\,\,a\\a=\frac{75.5}{225} \,\frac{m}{s^2} \\a=0.3356\,\,\frac{m}{s^2}$

7 0

2 years ago

the pull of gravity on mars is 3.7m/s^2. if a astronaut on mars lifts a 10 kg rock 1 m off the ground, just to see whats under i

Elanso [62]

Gravitational potential energy can be calculated using the formula:

$PE_{grav} =mgh$

Where:
PEgrav = Gravitational potential energy
m= mass
g = acceleration due to gravity
h = height

On Earth acceleration due to gravity is a constant 9.8 but since the scenario is on Mars, the pull of gravity is different. In this case, it is 3.7, so we will use that for g.

So put in what you know and solve for what you don't know.
m = 10kg
g = 3.7m/s^2
h = 1m

So we put that in and solve it.
$PE_{grav} =mgh$
$PE_{grav} =(10kg)(3.7m/s^{2})(1m)$
$PE_{grav} =37J$

7 0

3 years ago

You push your couch a distance of 3.9 m across the living room floor with a horizontal force of 220.0 n. the force of friction i

Mrac [35]

The general formula to calculate the work is:

$W=Fd \cos \theta$

where F is the force, d is the displacement of the couch, and $\theta$ is the angle between the direction of the force and the displacement. Let's apply this formula to the different parts of the problem.

(a) Work done by you: in this case, the force applied is parallel to the displacement of the couch, so $\theta=0^{\circ}$ and $\cos \theta=1$ , therefore the work is just equal to the product between the horizontal force you apply to push the couch and the distance the couch has been moved:

$W=Fd=(220.0 N)(3.9 m)=858 J$

(b) work done by the frictional force: the frictional force has opposite direction to the displacement, therefore $\theta=180^{\circ}$ and $\cos \theta=-1$ . Therefore, we must include a negative sign when we calculate the work done by the frictional force:

$W=-Fd=-(144.0 N)(3.9 m)=-561.6 J$

(c) The work done by gravity is zero. In fact, gravity (which points downwards) is perpendicular to the displacement of the couch (which is horizontal), therefore $\theta=90^{\circ}$ and $\cos \theta=0$ : this means

$W=0$ .

(d) Work done by the net force:

The net force is the difference between the horizontal force applied by you and the frictional force:

$F=220 N-144 N=76 N$

And the net force is in the same direction of the displacement, so $\theta=0^{\circ}$ and $\cos \theta=1$ and the work done is

$W=Fd=(76 N)(3.9 m)=296.4 J$

4 0

3 years ago