Why can’t we see black holes? Question 11 options: A.Because they don't want to be seen. B.Because the sun is too far away from
1 answer:
We can't see black holes because D) no light can get out
Explanation:
Black holes are the result of the gravitational collapse of a supermassive star.
The life of a supermassive star ends with a huge explosion, called supernova, that leaves behing a super-dense core called black hole.
Black holes are the most dense objects of the universe, having a huge mass in a super small size. For this reason, the gravitational force exerted by a black hole in its proximity is so strong that even light is not able to escape from the gravitational field. For this reason, light from a black hole is not able to reach us, and so we are not able to see these objects.
The "edge" of space beyond which light remains "trapped" inside the black hole is called event horizon, and no object can escape this region of space.
The radius of the event horizon of a black hole is called Schwarzschild radius and it is given by:
where
G is the gravitational constant
M is the mass of the black hole
c is the speed of light
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1) See graph in attachment
2) 10 s
3) 50 m
Explanation:
1)
In this problem, we have an object initially moving with a velocity of
v = 10 m/s
when the time is
t = 0 s
Then, we are told that the speed of the object is decreasing by 1 m/s every second. This means that on a velocity-time graph, the motion will be represented by a straight line, starting from v = 10 when t = 0, and decreasing by 1 m/s every second.
The result can be found in the graph in attachment.
Moreover, we can also infer that the motion of the object is accelerated (because velocity is changing), and that the acceleration is constant and it is equal to
which is equivalent to the gradient of the line in the velocity-time graph.
2)
In this part, we want to find after what time the body will stop its motion.
To do that, we can use the following suvat equation:
where
v is the final velocity
u is the initial velocity
a is the acceleration
t is the time
In this problem:
u = 10 m/s is the initial velocity of the body
is the acceleration
v = 0 m/s, because we want to find the time T at which the body will stop
Re-arranging the equation, we find:
3)
In order to find the total distance covered by the body during its accelerated motion, we have to use another suvat equation:
where
s is the distance covered
u is the initial velocity
t is the time
a is the acceleration
In this problem:
u = 10 m/s is the initial velocity
is the acceleration
t = 10 s is the time it takes for the body to stop (found in part 2)
Solving for s, we find the distance covered:
