Answer:
The value is 
Explanation:
From the question we are told that
The speed of in a vacuum is 
The speed of light in the material is 
Generally the reflection of the material is mathematically represented as

=> 
=> 
Answer:
There is a thing called a continental drift. It started about 200 million years ago. At first the continents were all attached, this super continent was called pangaea. Continental drift occurs because of the shift of the tectonic plates within the earth's outer shell. The heat from within the earth triggers movement to occur. This a very slow process though. It took 200 million years for the continents to get where the are now and would probably take another 200 to collide.
Answer:
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<h2><u><em>
D</em></u></h2>
Explanation:
3) For a displacement time graph, straight line denotes constant speed. For a velocity time graph, the graph parallel to time axis denotes constant speed. Hence, the correct option is a) and d).
Answer:
274N 0.41
Explanation:
As he is sliding down in a constant speed then the force that accelerates him (weight) and the force that slows his down (friction) are equal.
then
<em>friction=mass x gravity x sin(21)</em>
Fr=78kg x 9.8m/s2 x sin(21)=274N
<em>friction= coefficient of kinetic friction x normal force of from the slope</em>
Fr= u x 78kg x 9.8m/s2 x cos(21)=274N
Fr= u x 78kg x 9.8m/s2 x cos(21)=274Nu=274/677=0.41