Answer:
2.28 s
Explanation:
Let g = 9.8 m/s2 and neglect air resistance. The box of sand with an initial velocity of 4.2m/s in free fall would yield the following equation of motion
t = 2.28 or t = -3.14
Since t can only be positive we will pick t = 2.28
s
Mass is a property of the object. It doesn't depend on anything else,
and it doesn't change when the object goes to different places.
Its mass is always the same.
If it's 20,000 kilograms on Earth, then it's 20,000 kilograms on the
Moon, on Mars, in school, in bed, in love, in trouble, in water,
on Pluto, on Halley's comet, or in free fall in outer space.
That's why choice-B is the correct choice.
Now, if the question was talking about WEIGHT, then we would have
a lot to talk about, because WEIGHT depends on where you are, and
what else is around you. But mass doesn't.
Answer:
a) I = 1,894 10¹⁰ W / m², b) E = 1.376 10⁵ N / C
Explanation:
a) intensity is defined as energy per unit area per unit time
I = P / A
let's reduce the magnitudes to the SI system
P = 10 mW = 10 10⁻³ W
d = 0.82 μm = 0.82 10⁻⁶ m
the laser area is
A =π r² = π d²/4
A =π (0.82 10⁻⁶)²/4
A = 5.28 10⁻¹³ m²
we calculate
I = 
I = 1,894 10¹⁰ W / m²
b) average intensity and electric field are related
I = E * E
E = √I
E = 
E = 1.376 10⁵ N / C
The 4ohm resistor is not parallel to any devices, so the current through it is the same as the total current through the circuit.
Apply I = V/R
I = total current, V = battery voltage, R = total resistance
Calculate the total resistance R of the circuit first.
R will be the sum of the 4ohm resistor and the resistance of the 5&9ohm parallel resistors. To find the resistance of the pair, you apply the “sum of inverses” rule:
R = 1/(1/5 + 1/9) = 3.21ohm
Now add the 4ohm resistor:
R = 3.21 + 4 = 7.21ohm
Now let’s calculate I = V/R:
Given values:
V = 6.0V
R = 7.21ohm
Plug in and solve for I:
I = 6.0/7.21
I = 0.83A
