Explanation:
Red, green, and blue are therefore called additive primaries of light. ... When you block two lights, you see a shadow of the third color—for example, block the red and green lights and you get a blue shadow. If you block only one of the lights, you get a shadow whose color is a mixture of the other two.
First, your definition of a shadow is incorrect. A shadow is an area that receives less light than its surroundings because a specific source of light is blocked by whatever is "casting" the shadow. Your example of being outside reveals this. The sky and everything around you in the environment (unless you are surrounded by pitch black buildings) is sending more than enough light into your shadow, to reveal the pen to your eyes. The sky itself diffuses the sunlight everywhere, and the clouds reflect plenty of light when they are not directly in front of the Sun.
If you are indoors and have two light bulbs, you can throw two shadows at the same time, possibly of different darknesses, depending on the brightness of the light bulbs.
It can take a lot of work to get a room pitch black. One little hole or crack in some heavy window curtains can be enough to illuminate the room. There are very few perfectly dark shadows.
Work is done when a force is in the same direction as the object moves.
Explanation:
The work done by a force in moving an object is given by the equation
where
F is the magnitude of the force
d is the displacement of the object
is the angle between the directions of F and d
From the equation, we notice the following:
- Work is done by a force when the force is in the same direction as the object moves. In fact, in this case,
, and so 
, which means that the work done simply becomes 
- When the force is perpendicular to the motion of the object,
and 
, which means that no work done - Technically, work is also done when the force is not parallel to the motion of the object: in this case, the factor
means that only the component of the force parallel to the direction of motion contributes to do work on the object.
Therefore, the correct answer is
Work is done when a force is in the same direction as the object moves.
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Answer: thickness h = 0.014cm
Question: In the manufacturing of computer chips, cylinders of silicon are cut into thin wafers that are 3.30 inches in diameter and have a mass of 1.50 g of silicon. How thick (mm) is each wafer if silicon has a density of 2.33 g/cm 3 ? (The volume of a cylinder is V=πr 2 h )
Explanation:
The volume of a cylinder is
Volume V = πr^2h ....1
The density of a material is
Density D = mass m / volume V
D = m/V ....2
Since m and D are given, we can make V the subject of formula.
V = m/D ....3
From equation 1, we need to derive the thickness h of the cylindrical silicon.
h = V/πr^2 .....4
Substituting equation 3 into 4
h = (m/D)/πr^2 .....5
Given.
mass m = 1.50g
density D = 2.33g/cm^3
radius r = diameter/2 = 3.00in/2 = 7.62/2 cm = 3.81cm
Substituting the given values into the equation
h = (1.5/2.33)/(π ×3.81^2)
thickness h = 0.014cm
The following lists of
stars in order from least density to greatest density are giant, main sequence
star, white dwarf, neutron star. The answer is letter B. Aside from neutron
star being the densest star, it is also the smallest star compared to the giant
star, as its name implied.
