Cosmic ray visual phenomena, or "light flashes" (LF), are spontaneous flashes of light visually perceived by some astronauts outside the magnetosphere of the Earth, such as during the Apollo program. While LF may be the result of actual photons of visible light being sensed by the retina,[1] the LF discussed here could also pertain to phosphenes, which are sensations of light produced by the activation of neurons along the visual pathway.[2]
Astronauts have long reported the experience of seeing flashes while they are in space, even when their eyes are closed. Neil Armstrong and Buzz Aldrin both reported these flashes during the Apollo 11 mission, and similar reports during the Apollo 12 and 13 missions led to subsequent Apollo missions including experiments specifically looking at this strange phenomenon.
Answer:
a) W = - 6.825 J, b) θ = 1.72 revolution
Explanation:
a) In this exercise the work of the friction force is negative and is equal to the variation of the kinetic energy of the particle
W = ΔK
W = K_f - K₀
W = ½ m v_f² - ½ m v₀²
W = ½ 0.325 (5.5² - 8.5²)
W = - 6.825 J
b) find us the coefficient of friction
Let's use Newton's second law
fr = μ N
y-axis (vertical) N-W = 0
fr = μ W
work is defined by
W = F d
the distance traveled in a revolution is
d₀ = 2π r
W = μ mg d₀ = -6.825
μ =
The total work as the object stops the final velocity is zero v_f = 0
W = 0 - ½ m v₀²
W = - ½ 0.325 8.5²
W = - 11.74 J
μ mg d = -11.74
we subtitle the friction coefficient value
( ) m g d = -11.74
6.825 = 11.74
d = 11.74/6.825 d₀
d = 1.7201 2π 0.400
d = 4.32 m
this is the total distance traveled, the distance and the angle are related
θ = d / r
θ = 4.32 / 0.40
θ = 10.808 rad
we reduce to revolutions
θ = 10.808 rad (1rev / 2π rad)
θ = 1.72 revolution
#9). the <em>last </em>statement is true
Calculation using Ohm's Law:
It helps a lot if you know what Ohm's Law says.
It says: Current = (voltage) / (resistance)
Current = (500 volts) / (250 ohms)
<em>Current = 2 Amperes</em>