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3 years ago

Why does your hand feel cool if you spill some alcohol on it?

2 answers:

6 0

It takes heat to make something evaporate, so it takes heat from your arm. Alcohol easily evaporates at room temperature, so it feels cool. This is also why you feel cool when getting out of the pool. The water on your skin evaporates.

Evgesh-ka [11]3 years ago

6 0

The heat transfers from your warm hand to the alcohol. The energy leaving your hand causes it to “feel cold.”

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Conductivity in a metal results from the metal atoms having

maks197457 [2]

Answer: A) highly mobile electrons in the valence shell

Explanation: conductivity in metals is a result of the movement of electrically charged particles—the electrons. These free electrons also known as valence electrons are free to move, and as a result they can travel through the lattice that forms the physical structure of a metal. The presence of valence electrons determines a metal's conductivity. However, several other factors can affect the conductivity of a metal such as impurities, temperature, magnetic fields etc.

5 0

3 years ago

un avión aterriza en la superficie de un portaaviones a 50 m/s y se detiene por completo en 120 metros, ¿cuál es la aceleración

sergejj [24]

Answer:

La aceleración necesaria para detener el avión es - 10.42 m/s².

Explanation:

Un movimiento uniformemente acelerado (M.U.A) es aquél cuya aceleración es constante y la velocidad de un objeto cambia a medida que el movimiento evoluciona.

Siendo la aceleración "a" el cambio de velocidad al tiempo transcurrido en un punto A a B, la velocidad inicial la velocidad que tiene un cuerpo al iniciar su movimiento en un período de tiempo y la velocidad final la velocidad que tiene un cuerpo al finalizar su movimiento en un período de tiempo, entonces en M.U.A se cumple:

Vf² - Vo² = 2*a*d

donde:

Vf: Velocidad final
Vo: Velocidad inicial
a: Aceleración
d: Distancia recorrida

En este caso:

Vf: 0 m/s, porque el avión se detiene
Vo: 50 m/s
a: ?
d: 120 m

Reemplazando:

(0 m/s)² - (50 m/s)² = 2*a*120 m

Resolviendo:

$a=\frac{(0 m/s)^{2} -(50 m/s)^{2} }{2*120 m}$

a= - 10.42 m/s²

La aceleración necesaria para detener el avión es - 10.42 m/s².

5 0

2 years ago

Why is oxygen more chemically reactive than nitrogen?

grin007 [14]

Answer:

O2 has two more electrons compared to N2, with extra 2 electrons in the higher energy anti-bonding orbitals known as Diradical. These electrons have higher energy and are unpaired; therefore, O2 is more reactive

Explanation:

5 0

2 years ago

Read 2 more answers

A railroad car moves under a grain elevator at a constant speed of 3.20 m/s. Grain drops into the car at the rate of 240 kg/min.

dedylja [7]

Answer:

F = 768 N

Explanation:

It is given that,

Speed of the elevator, v = 3.2 m/s

Grain drops into the car at the rate of 240 kg/min, $\dfrac{dm}{dt}=240\ kg/min = 4\ kg/s$

We need to find the magnitude of force needed to keep the car moving constant speed. The relation between the momentum and the force is given by :

$F=\dfrac{dp}{dt}$

$F=m\dfrac{dv}{dt}+v\dfrac{dm}{dt}$

Since, the speed is constant,

$F=m\dfrac{dv}{dt}$

$F=v\dfrac{dm}{dt}$

$F=3.2\times 240$

F = 768 N

So, the magnitude of force need to keep the car is 768 N. Hence, this is the required solution.

5 0

3 years ago

Due to efficiency considerations related to its bow wake, the supersonic transport aircraft must maintain a cruising speed that

givi [52]

Answer:

decreases.

Explanation:

When the aircraft is flies from the warm air into the colder air then its speed will be decreases.

as we know that

we know mach number is constant

so that here Mach number M is expressed as

M = $\frac{u}{v}$ .............................1

here u is Local flow velocity with respect to the boundarie and v is the speed of sound in the medium

If the aircraft flies from hot air to cold air, the speed of sound in the medium will decrease. But the Mach number remains constant. Therefore, the local flow velocity relative to the boundaries also decreases.

7 0

3 years ago