Answer:
I = W / 4π R_{s}², P = W / 2π c R_{s}², Io /I_{earth} = 10⁴
Explanation:
The intensity is defined as the ratio between the emitted power and the area of the spherical surface
I = P / A
Since the emitted power is constant and has a value of W for this case, let's look for the area of the sphere on the surface of the sun
A = 4π 
²
I = W / 4π R_{s}²
.- The radiation pressure for total absorption is
P = S / c
Where S is the Pointer vector that is equal to the intensity
Let's replace
P = W / 2π c R_{s}²
.- We repeat for r = R_{s}/2
I₂ = W / 4π (R_{s}/ 2)²
I₂ = 4 W / 4π R_{s}²
I₂ = 4 Io
I₀ = W / 4piRs2
We calculate the radiation pressure
P₂ = I₂ / c
P₂ = 4 I₀ / c
P₂ = 4 (W / 4pi c Rs2)
.- the relationship between these magnitudes is
I₂ / I₀ = 4
P₂ / P₀ = 4
Let's calculate the intensity on the surface where the Earth is
r = 1.50 10¹¹ m
= W / 4π r²
Io / I_{earth} = r² /²
Io /I_{earth} = (1.5 10¹¹ / 6.96 10⁸) 2
Io /I_{earth} = 4.6 10⁴
Io /I_{earth} = 10⁴
Answer:
A) It takes the truck 8 s to catch the motorcycle.
B) The motorcycle has traveled 160 m in that time.
C) The velocity of the truck is 40 m/s at that time.
Explanation:
The equations of the position and velocity of an object moving in a straight line are as follows:
x = x0 +v0 · t + 1/2 · a · t²
v = v0 + a · t
Where:
x = position
x0 = initial position
v0 = initial velocity
t = time
a = acceleration
v = velocity at time t
(A) When the the truck catches the motorcycle, both have the same position. Notice that the motorcycle moves at constant speed so that a = 0:
x truck = x motorcycle
x0 +v0 · t + 1/2 · a · t² = x0 + v · t
Placing the origin of the frame of reference at the point where the truck starts, both have an initial position of 0. The initial velocity of the truck is 0. Then:
1/2 · a · t² = v · t
solving for t:
t = 2 v/a
t = 2 · 20 m/s/ 5 m/s²
t = 8 s
It takes the truck 8 s to catch the motorcycle.
(B) Using the equation of the position of the motorcycle, we can calculate the traveled distance in 8 s.
x = v · t
x = 20 m/s · 8 s
x = 160 m
(C) Now, we use the velocity equation at time 8 s.
v = v0 + a · t
v = 0 m/s + 5 m/s² · 8 s
v = 40 m/s
Answer:
heat energy
Explanation:
Friction causes the molecules on rubbing surfaces to move faster, so they have more energy. This gives them a higher temperature, and they feel warmer.
