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2 years ago

Why does water feel cool when it evaporates

2 answers:

5 0

Basically, when water evaporates, it always absorbs energy. What happens is that a molecule steals surface energy for all molecules until it is hot enough to evaporate. This is how the evaporation process happens. For this reason, the surface cools because the molecules steal the heat from the medium. This can easily be noticed when we sweat and after the water molecules evaporate from our body, it cools.

Illusion [34]2 years ago

4 0

First, it makes your skin feel cooler when it's wet. And when it evaporates it removes some heat. But sweat will only evaporate in an environment where there isn't muchwater in the air. In a place with high humidity, there're already lots of water molecules in the air.

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A man paddles a canoe at 6 km per hour. If he paddles on a river with a current of 6 km per hour, what is the speed of the canoe

Romashka-Z-Leto [24]

Answer:

If the canoe heads upstream the speed is zero. And directly across the river is 8.48 [km/h] towards southeast

Explanation:

When the canoe moves upstream, it is moving in the opposite direction of the normal river current. Since the velocities are vector (magnitude and direction) we can sum each vector:

Vr = velocity of the river = 6[km/h}

Vc = velocity of the canoe = -6 [km/h]

We take the direction of the river as positive, therefore other velocity in the opposite direction will be negative.

Vt = Vr + Vc = 6 - 6 = 0 [km/h]

For the second question, we need to make a sketch of the canoe and we are watching this movement at a high elevation. So let's say that the canoe is located in point 0 where it is located one of the river's borders.

So we are having one movement to the right (x-direction). And the movement of the river to the south ( - y-direction).

Since the velocities are vector we can sum each vector, so using the Pythagoras theorem we have:

$Vt = \sqrt{(6)^{2} +(-6)^{2} } \\Vt=8.48[km/h]$

5 0

2 years ago

Explain why xrays are used to take images of inside the body but UV isnt

Sidana [21]

Answer:

X-rays go all the way through the body, but ultraviolet rays do not.

Explanation:

An x-ray will show inside the body, but uv light isn't strong enough to go all the way through the body.

6 0

2 years ago

A jet aircraft is traveling at 262 m/s in hor-

NeTakaya

Solution :

Speed of the air craft, $S_a$ = 262 m/s

Fuel burns at the rate of, $S_b$ = 3.92 kg/s

Rate at which the engine takes in air, $S_{air}$ = 85.9 kg/s

Speed of the exhaust gas that are ejected relative to the aircraft, $S_{exh}$ =921 m/s

Therefore, the upward thrust of the jet engine is given by

$F=S_{air}(S_{exh}-S_a)+(S_b \times S_{exh})$

F = 85.9(921 - 262) + (3.92 x 921)

= 4862635.79 + 3610.32

= $4.8 \times 10^6 \ N$

Therefore thrust of the jet engine is $4.8 \times 10^6 \ N$ .

3 0

2 years ago

What type of energy is formed when an object encounters friction?

kiruha [24]

Answer:

thermal energy

Friction does negative work and removes some of the energy the person expends and converts it to thermal energy. The net work equals the sum of the work done by each individual force. The forces acting on the package are gravity, the normal force, the force of friction, and the applied force.

Explanation:

6 0

2 years ago

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What casues leaves to change color in autam

Furkat [3]

Answer: Chlorophyll Breaking down.

Explanation: When it starts to get cooler the chlorophyll breaks down causing the pretty green color to change to brown gold and orange.

3 0

2 years ago

Read 2 more answers