Answer:
The answer is convection.
Explanation:
There are three types of heat transfer: conduction, convection and radiation.
- Conduction occurs when two objects touch each other and transfer heat.
- Convection occurs when an object heats its surrounding fluid (like air, or water) and, since the hot fluids are less dense than the cold ones, they go up. So convection is a type of heat transfer that usually goes from down to up.
- Radiation occurs when objects emanate heat in the form of electromagnetic waves that propagates in all directions.
So in this case, when the marshmallow is above the fire, it is exposed to convection, which does not occur when it is on the side of the fire.
Answer:
Distance: -30.0 cm; image is virtual, upright, enlarged
Explanation:
We can find the distance of the image using the lens equation:

where:
f = 15.0 cm is the focal length of the lens (positive for a converging lens)
p = 10.0 cm is the distance of the object from the lens
q is the distance of the image from the lens
Solving for q,

The negative sign tells us that the image is virtual (on the same side of the object, and it cannot be projected on a screen).
The magnification can be found as

The magnification gives us the ratio of the size of the image to that of the object: since here |M| = 3, this means that the image is 3 times larger than the object.
Also, the fact that the magnification is positive tells us that the image is upright.
Via half-life equation we have:

Where the initial amount is 50 grams, half-life is 4 minutes, and time elapsed is 12 minutes. By plugging those values in we get:

There is 6.25 grams left of Ra-229 after 12 minutes.
The formula relevant for this is:
h = v0t + 0.5 gt^2
since the rock was dropped, therefore:
h = 0.5 gt^2
we can see that:
h / t^2 = 0.5 g = constant
therefore:
4.9 m / (1 s)^2 = h / (3 s)^2
<span>h = 44.1 m </span>
Answer:
t = 4.21x10⁻⁷ s
Explanation:
The time (t) can be found using the angular velocity (ω):
<em>Where θ: is the angular displacement = π (since it moves halfway through a complete circle)</em>
We have:
<u>Where</u>:
<em>v: is the tangential speed </em>
<em>r: is the radius</em>
The radius can be found equaling the magnetic force with the centripetal force:

Where:
m: is the mass of the alpha particle = 6.64x10⁻²⁷ kg
q: is the charge of the alpha particle = 2*p (proton) = 2*1.6x10⁻¹⁹C
B: is the magnetic field = 0.155 T
Hence, the time is:

Therefore, the time that takes for an alpha particle to move halfway through a complete circle is 4.21x10⁻⁷ s.
I hope it helps you!