A radar used to detect the presence of aircraft receives a pulse that has reflected off an object 5 ✕ 10−5 s after it was transm
1 answer:
Answer:
7500 m
Explanation:
The radar emits an electromagnetic wave that travels towards the object and then it is reflected back to the radar.
We can call L the distance between the radar and the object; this means that the electromagnetic wave travels twice this distance, so
d = 2L
In a time of
Electromagnetic waves travel in a vacuum at the speed of light, which is equal to
Since the electromagnetic wave travels with constant speed, we can use the equation for uniform motion ,so:
(1)
where
, where L is the distance between the radar and the object
Re-arranging eq(1) and substituting, we find L:
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Answer:
35 288 mile/sec
Explanation:
This is a problem of special relativity. The clocks start when the spaceship passes Earth with a velocity v, relative to the earth. So, out and back from the earth it will take:
If we use the Lorentz factor, then, as observed by the crew of the ship, the arrival time will be:
Then the amount of time wil expressed as a reciprocal of the Lorentz factor. Thus:
solving for v, gives = 35 288 miles/s
Answer: Dalton’s model
Explanation:
In the attached image we can see four atomic models labeled with four letters:
W represents the current and accepeted atomic model: a nucleus with an electron cloud, where the orbit and position of the electrons around the nucleus is defined by specific regions (associated with specific energy levels) where there is a greater probability of finding the electron at any given moment. It is important to note this model was improved by the works in quantum physics done by Louis de Broglie and Erwin Schrodinger.
X represents Rutherford's model (This model was proposed after Thomson's model). Ernest Rutherford conducted a series of experiments in order to corroborate Thomson's atomic model. However the results of the experiment led him to find out there is a concentration of charge in the atom's core (which was later called nucleus) surrounded by electrons. This lead to a new atomic model, in which the atom has a positive charged nucleus surrounded by negative charged particles that move similar to the orbit of the planet around the Sun.
Y represents Thomson's model, also called the <em>plum pudding</em> model. This scientific found out that atoms contain small subatomic particles with a negative charge (later called electrons). However, taking into consideration that at that time there was still no evidence of the atom nucleus, Thomson thought the electrons were immersed in the atom of positive charge that counteracted the negative charge of the electrons. Just like the raisins embedded in a pudding or bread.
Z represents Bohr's model. This model was proposed by the danish physicist Niels Bohr after Rutherford's model. In fact, this model was Rutherford's model with the following addition: electrons orbit the nucleus (like planets around the sun) in specific orbits at different energy levels around the nucleus.
So, the only missing model is <u>Dalton's model</u>, which was the first atomic model: the atom represented as a solid, indestructible and indivisible mass. An idea that was already accepted by that time since the ancient Greeks.
