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2 years ago

Please I need help with this question (see image).Show workings if necessary

Physics

1 answer:

timofeeve [1]2 years ago

5 0

<h2><u>Question</u> :</h2>

When an athlete perspires after running

Evaporation occurs and helps to cool the body.
Convection cools the body.
The body absorbs cold from the surrounding air.
Heat is conducted away from the body.

<h2><u>Answer</u> :</h2>

When an athlete perspires after running evaporation occurs and helps to cool the body.

Correct option is A.

<h2><u>Explanation</u> :</h2>

When an athlete perspires after running then sweat evaporates and we know that evaporation causes cooling as evaporation requires heat energy. The required heat energy is taken away by the molecules of sweat when they convert from liquid into gas, and this causes cooling on the surface of body. That's why it helps to cool the body.

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An above ground swimming pool of 30 ft diameter and 5 ft depth is to be filled from a garden hose (smooth interior) of length 10

STALIN [3.7K]

This question involves the concepts of dynamic pressure, volume flow rate, and flow speed.

It will take "5.1 hours" to fill the pool.

First, we will use the formula for the dynamic pressure to find out the flow speed of water:

$P=\frac{1}{2}\rho v^2\\\\v=\sqrt{\frac{2P}{\rho}}$

where,

v = flow speed = ?

P = Dynamic Pressure = 55 psi $(\frac{6894.76\ Pa}{1\ psi})$ = 379212 Pa

$\rho$ = density of water = 1000 kg/m³

Therefore,

$v=\sqrt{\frac{2(379212\ Pa)}{1000\ kg/m^3}}$

v = 27.54 m/s

Now, we will use the formula for volume flow rate of water coming from the hose to find out the time taken by the pool to be filled:

$\frac{V}{t} = Av\\\\t =\frac{V}{Av}$

where,

t = time to fill the pool = ?

A = Area of the mouth of hose = $\frac{\pi (0.015875\ m)^2}{4}$ = 1.98 x 10⁻⁴ m²

V = Volume of the pool = (Area of pool)(depth of pool) = A(1.524 m)

V = $[\frac{\pi (9.144\ m)^2}{4}][1.524\ m]$ = 100.1 m³

Therefore,

$t = \frac{(100.1\ m^3)}{(1.98\ x\ 10^{-4}\ m^2)(27.54\ m/s)}\\\\$

<u>t = 18353.5 s = 305.9 min = 5.1 hours</u>

Learn more about dynamic pressure here:

brainly.com/question/13155610?referrer=searchResults

7 0

2 years ago

Find the angle for the third-order maximum for 591 nm wavelength light falling on a diffraction grating having 1460 lines per ce

Marat540 [252]

Answer:

15.32°

Explanation:

We have given the wavelength $\lambda =591nm=591\times 10^{-9}m$

Diffraction grating is 1460 lines per cm

So $d=\frac{10^{-2}}{1460}=6.71\times 10^{-6}m$ (as 1 m=100 cm )

For maximum diffraction

$dsin\Theta =m\lambda$ here m is order of diffraction

So $6.71\times 10^{-6}sin\Theta =3\times 591\times 10^{-9}$

$sin\Theta =0.264$

$\Theta =15.32^{\circ}$

6 0

2 years ago

A 5.00 kilogram block slides along a horizontal,frictionless surface at 10.0 meters per second. for 4.00 seconds. The magnitude

finlep [7]

In this question a lot of information's are provided. Among the information's provided one information and that is the time of 4 seconds is not required for calculating the answer. Only the other information's are required.
Mass of the block that is sliding = 5.00 kg
Distance for which the block slides = 10 meters/second
Then we already know that
Momentum = Mass * Distance travelled
= (5 * 10) Kg m/s
= 50 kg m/s
So the magnitude of the blocks momentum is 50 kg m/s. The correct option among all the given options is option "b".

5 0

3 years ago

A sewing machine uses 1.6kWh of electricity in one day. If electricity costs 9p per unit, what is the total cost in pence of usi

atroni [7]

Answer:

$\huge\boxed{\sf 1.6\ units = 14.4p}$

Explanation:

Since,

So,

1.6 kWh = 1.6 units

If,

1.6 units = 9p × 1.6

1.6 units = 14.4p

$\rule[225]{225}{2}$

8 0

1 year ago

Give 5 examples of physical properties that could be used to describe a solid

ycow [4]

1.) appearance
2.)texture
3.)color
4.)melting point
5.)odor

8 0

3 years ago

Please I need help with this question (see image).Show workings if necessary​

Please I need help with this question (see image).Show workings if necessary