Answer:
You are exactly right. The molecules in hot air are moving faster than the molecules in cold air. Because of this, the molecules in hot air tend to be further apart on average, giving hot air a lower density. That means, for the same volume of air, hot air has fewer molecules and so it weighs less
 
        
             
        
        
        
Answer: 
I think the answer is 
C) iron nails are attracted towards all materials
        
             
        
        
        
Answer:
N = 1364 N
Explanation:
given data 
accelerate upward = 5.70 m/s²
mass = 88.0 kg
solution 
normal force is in upward direction so, weight of the student in downward direction and acceleration is in upward direction so formula is express as 
N - mg = ma        ...........................1 
N = m × (g+a) 
put here value 
N = 88.0 × (9.8 + 5.70) 
N = 1364 N
 
        
             
        
        
        
It is false. Because the amount of energy carried in the wave is inversely related to the length of the waves wavelength. To correct the statement it should be that the shorter the radiation's wavelength the stronger is the radiation's energy.