Gravity, friction, and air resistance are some examples.
The phrase "light year" is a <u><em>distance</em></u> ... it's the distance that light travels through vacuum in one year.
When you look at an object located 1 light year away from you, you see it as it was 1 year ago.
If a star located 10 light years away from us suddenly brightens, or dims, or explodes, we see the event <em>10 years later.</em>
answer:
an opaque object is one that doesn't let light pass through it. instead, it reflects or absorbs the light that strikes it.
explanation:
in this case, we see the material because of the transmitted light. therefore, the wavelength of the transmitted light determines the color that the object appears.
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Answer:
(a) -472.305 J
(b) 1 m
Explanation:
(a)
Change in mechanical energy equals change in kinetic energy
Kinetic energy is given by
Initial kinetic energy is 
Since he finally comes to rest, final kinetic energy is zero because the final velocity is zero
Change in kinetic energy is given by final kinetic energy- initial kinetic energy hence
0-472.305 J=-472.305 J
(b)
From fundamental kinematic equation

Where v and u are final and initial velocities respectively, a is acceleration, s is distance
Making s the subject we obtain
but a=\mu g hence

Its D that so easy look at it