Answer:581.87 K
Explanation:
Given
Sphere is melted to form a square
Let the radius of sphere be r and square has a side a
Therefore

Surface area of sphere 
Surface area of cube 
Total emmisive remains same
Thus 







Answer:
The speed of light changes as it moves between media. This causes refraction. Angles of refraction can be calculated using known speeds or wavelengths. Beyond the critical angle, light is reflected.
Force applied on the car due to engine is given as
towards right
Also there is a force on the car towards left due to air drag
towards left
now the net force on the car will be given as

now we can say that since the two forces are here opposite in direction so here the vector sum of two forces will be the algebraic difference of the two forces.
So we can say



So here net force on the car will be 150 N towards right and hence it will accelerate due to same force.
Answer: A
Explanation: We know that f=p*n
f=50*300=15000 Hz = 15kHz.
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