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3 years ago

Identify the true statement. Choose one:

Physics

1 answer:

beks73 [17]3 years ago

4 0

Answer:

A. Underground coal mining is dangerous because of possible tunnel collapse and possible methane gas explosions.

Explanation:

Dangers of underground coal mining include asphyxiation, methane gas poisoning, tunnel collapse and explosions of methane gas, a highly flammable gas. Methane explosions occur since this gas is a byproduct of coal. This explosion can cause tunnel collapse.

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When someone leaves an outside door open on a cold, still day, it is often said that the person is letting in cold air. If so, h

Vikentia [17]

Answer:

Diffusion

Explanation:

This process can be referred to as diffusion. The cold air moves from a region of high concentration (outside) to a region of low concentration (inside). The movement of these cold air is what is referred to as "letting in cold air".

NOTE: Diffusion is the process in which substances move from a region of high concentration to a region of low concentration. Just like when an insecticide is sprayed inside a closed room and then the room is later opened so as to allow the the sprayed insecticide leave the room.

8 0

4 years ago

A 15.0 kilogram cart initially traveling at 2.0 meters per second east accelerates uniformly at 0.75 meter per second squared ea

Montano1993 [528]

Answer:

Explanation:

Since this is not parabolic motion, it is one-dimensional motion. Very simple. What we are given is

mass: 15.0 kg

initial velocity: 2.0 m/s

acceleration: .75 m/s/s

time: 6.0 seconds

Since we are looking for final velocity, the equation we need for this is

v = v0 + at that says final velocity is equal to the initial velocity plus the acceleration of the object times how long it travels. We don't have a need for the mass here at all.

$v=2.0\frac{m}{s}+.75\frac{m}{s^2}(6.0s)$

Notice that one of the seconds labels to the right of the plus sign cancel out, leaving us with like units...which we HAVE to have if we want to add.

Simplifying a bit gives us

v = 2.0 m/s + 4.5 m/s so

v = 6.5 m/s

4 0

3 years ago

Find the ratio of the diameter of aluminium to copper wire, if they have the same

kicyunya [14]

Answer:

1.24

Explanation:

The resistivity of copper $\rho_1=2.65\times 10^{-8}\ \Omega-m$

The resistivity of Aluminum, $\rho_2=1.72\times 10^{-8}\ \Omega-m$

The wires have same resistance per unit length.

The resistance of a wire is given by :

$R=\rho \dfrac{l}{A}\\\\R=\rho \dfrac{l}{\pi (\dfrac{d}{2})^2}\\\\\dfrac{R}{l}=\rho \dfrac{1}{\pi (\dfrac{d}{2})^2}$

According to given condition,

$\rho_1 \dfrac{1}{\pi (\dfrac{d_1}{2})^2}=\rho_2 \dfrac{1}{\pi (\dfrac{d_2}{2})^2}\\\\\rho_1 \dfrac{1}{{d_1}^2}=\rho_2 \dfrac{1}{{d_2}^2}\\\\(\dfrac{d_2}{d_1})^2=\dfrac{\rho_1}{\rho_2}\\\\\dfrac{d_2}{d_1}=\sqrt{\dfrac{\rho_1}{\rho_2}}\\\\\dfrac{d_2}{d_1}=\sqrt{\dfrac{2.65\times 10^{-8}}{1.72\times 10^{-8}}}\\\\=1.24$

So, the required ratio of the diameter of Aluminum to Copper wire is 1.24.

3 0

3 years ago

You drop a 6.0x10^-2 kg ball from height of 1.0m above hard flat surface. Ball strikes surface and energy decreases by 0.14J, th

harina [27]

If you drop a <span>6.0x10^-2 kg ball from height of 1.0m above hard flat surface, and a</span>fter the ball had bounce off the flat surface, the kinetic energy of the ball would be mgh - 0.14 = 0.45.

3 0

3 years ago

Read 2 more answers

What was the name of the first man made satellite launched by the Soviet Union in 1957.

OverLord2011 [107]

Answer:

In 1957 the Soviet union launched Sputnik , the first satellite in space...

6 0

3 years ago