The heating of the lower layer of the atmosphere from radiation absorbed by certain heat- absorbing gasses is called ?

Fill in the term that completes the statement. The north and south poles of a magnetic field produced by an electromagnet will s

Minchanka [31]

Answer:

when the direction of the Current changes.

Explanation:

Electromagnet refers to an iron ore wrapped around with a coil of wire, in presence of electric current. As it acts like a magnet, when current is passed through it.

The north & south poles of magnetic fields produced by such magnet, change with direction of current passed through it.

6 0

2 years ago

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a person throws a ball upward into the air with an initial velocity of 20 m/s. calculate (a) how high it goes, and (b) how long

Phantasy [73]

Answer:

a) about 20.4 meters high

b) about 4.08 seconds

Explanation:

Part a)

To find the maximum height the ball reaches under the action of gravity (g = 9.8 m/s^2) use the equation that connects change in velocity over time with acceleration.

$a=\frac{Vf-Vi}{t}$

$-9.8 \frac{m}{s} =\frac{Vf-Vi}{t}$

In our case, the initial velocity of the ball as it leaves the hands of the person is Vi = 20 m/s, while thw final velocity of the ball as it reaches its maximum height is zero (0) m/s. Therefore we can solve for the time it takes the ball to reach the top:

$-9.8 =\frac{0-20}{t}\\t=\frac{20}{9.8} s = 2.04 s$

Now we use this time in the expression for the distance covered (final position Xf minus initial position Xi) under acceleration:

$Xf-Xi=Vi*t+\frac{1}{2} a t^{2} \\Xf-Xi=20*(2.04)-\frac{1}{2} 9.8*2.04^{2}\\Xf-Xi=20.408 m$

Part b) Now we use the expression for distance covered under acceleration to find the time it takes for the ball to leave the person's hand and come back to it (notice that Xf-Xi in this case will be zero - same final and initial position)

$Xf-Xi=0=20*(t)-\frac{1}{2} 9.8*t^{2$

To solve for "t" in this quadratic equation, we can factor it out as shown:

$0= t(20-\frac{9.8}{2} t)$

Therefore there are two possible solutions when each of the two factors equals zero:

1) t= 0 (which is not representative of our case) , and

2) the expression in parenthesis is zero:

$0= 20-\frac{9.8}{2} t\\t=\frac{20*2}{9.8} = 4.08 s$

7 0

3 years ago

How long does it take to change a flat plain into mountains?

ss7ja [257]

It would take millions of years to form a mountain as plates move very slowly and to form it first one plate should climb upon another. After this very slowly this hill will convert into a mountain.

5 0

2 years ago

Which statements about our solar system are false?

morpeh [17]

The second statement is false. The Sun is a star, but not the only star.

6 0

2 years ago

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A student pushes a 12.0 kg box with a horizontal force of 20 N. The friction force on the box is 9.0 N. Which of the following i

Hoochie [10]

The acceleration of the box is approximately $1 m/s^2$