Explanation:
It is given that,
Diameter of the semicircle, d = 45 m
Radius of the semicircle, r = 22.5 m      
Speed of greyhound, v = 15 m/s
The greyhound is moving under the action of centripetal acceleration. Its formula is given by :



We know that, 


Hence, this is the required solution.                                                
 
        
             
        
        
        
Answer:
Option C, increases and decreases
Explanation:
When an object making noise approaches you, the wave frequency increases leading to a higher pitch. Conversely, when it moves away from you or retreats, the wave frequency decreases leading to a lower pitch. This can be observed in ambulance sirens.
 
        
             
        
        
        
Answer:633.8 KJ
Explanation:
Given
mass of water
Initial temperature
Final temperature 
Specific heat of water  =4190 J/kg-k
=4190 J/kg-k
heat of vaporization
Heat required for process =heat to raise water temperature from 20 to 100 +Heat to vapourize water completely
=heat to raise water temperature from 20 to 100 +Heat to vapourize water completely
Q=mc
Q=
Q=
Q=
 
        
             
        
        
        
Answer:
the answer is 
B)It was the first planet located through mathematical calculations
 
        
             
        
        
        
Answer:
The answer is a wedge.
Explanation:
The wedge is a combination of two inclined planes. It is used to separate bodies which are held together by large forces, e.g, splitting timber
 M.A.= slant height of wedge/thickness of wedge. 
 Hence a long thin wedge has a higher mechanical advantage than a short thick one; or the smaller the angle theta between the slant heights, the greater the mechanical advantage.