Using the principle of floatation.
u = w............(a)
Upthrust of fluid is equal to the weight of the object.
Let the volume of the wood be V.
The upthrust u, is related to the volume submerged in water, and that is 1/5 of it volume, that is (1/5)V = 0.2V
Formula for upthrust, u = vdg
where v = volume of fluid displaced
d = density of fluid
g = acceleration due to gravity
weight, w = mg
where m = mass
g = acceleration due to gravity 
From (a)
                     u = w
                 vdg =  mg      Cancel out g
                   vd  =  m
 
The v  is equal to 0.2V, which is the submerged volume. Notice that the small letter v is volume of fluid displaced, and capital V is the volume of the solid. 
d is density of fluid which is water in this case, 1000 kg/m³
         0.2V * 1000 =  m
           200V =  m
Hence the mass of the object is  200V  kg.
But Density of solid =  Mass of solid / Volume of solid
                                 =    200V / V
                                 =    200 kg/m³
Density of solid = 200 kg/m³      
        
             
        
        
        
The linear velocity of a rotating object is the product of the angular velocity and the radius of the circular motion. Angular velocity is the rate of the change of angular displacement of a body that is in a circular motion. It is a vector quantity so it consists of a magnitude and direction. From the problem, the angular velocity is 5.9 rad per second and the radius is given as 12 centimeters. We calculate as follows:
Linear velocity = angular velocity (radius)
Linear velocity = 5.9 (12 ) = 70.8 cm / s
The linear velocity of the body in motion is 70.8 centimeters per second or 0.708 meters per second.
        
             
        
        
        
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Answer:
A. Gamma radiation is an electromagnetic wave.
Explanation:
" Gamma ray is an electromagnetic radiation from a nucleus. It is not safe.
" Nucleus of a helium atom is called Alpha particle.
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Hope this answer can help you,
 
        
             
        
        
        
Answer:
But the Sun isn't actually yellow; it's just an illusion caused by the Earth's atmosphere. The powerful processes happening inside the Sun are so robust that it emits every color of light imaginable. Together, these colors form a pure white light, which is precisely what you'd see from space.
Hoped I helped