Answer:
a. when the acceleration of the objects become negative 
 
        
             
        
        
        
Answer:
Explanation:required formula is 
W 1=F*S
W1=work done by Sam =? 
F=force applied by sam=150N
S=displacement =10m
again 
W2=F*S
W2=work done by friction =? 
S=displacement =10m
F=friction =25N
W=W1-W2=net work done 
please feel free to ask if you have any questions 
 
        
             
        
        
        
Answer:
Hydraulic pressure exerted on glass slab, ρ=10 atm
Bulk modulus of glass, B=37×10^9 Nm^−2
 
Bulk modulus, B=P/(ΔV/V)
where, 
ΔV/V= Fractional change in volume
ΔV/V=P/B
 =10×1.013×10^5 /(37×10 ^9)
 
 =2.73×10^-5
 
Therefore, the fractional change in the volume of the glass slab is 2.73×10^-5
 Hope it helps
 
        
                    
             
        
        
        
Answer:
 Ptolemy proposed a model, he reference system is centered on the Earth
Copernicus, proposed a deferent system,  this system is centered on the Sun, where it is at the origin of the system
Explanation:
Thousands of years ago, Ptolemy proposed a model to explain the movement of the planets and stars in the sky, in this model the reference system is centered on the Earth, so each body is orbiting in different spheres around the Earth as its center, this system had very complicated calculations and curves to be able to explain the orbits of the planets.
More recently Copernicus, proposed a deferent system, this system is centered on the Sun, where it is at the origin of the system, in this system the movement of the planets are ellipses, which is a much simpler explanation and has been widely accepted, in current systems the reference system is fixed in the bodies more massive, since this simplifies the explanation of the movements.
 
        
             
        
        
        
Answer options:
A) Some connections are lost because critical stages of development were missed.
B) Some connections are lost so others can be strengthened.
C) Some connections are lost because of experimentation with drugs or alcohol.
D) Some connections are lost so that children become less dependent and are less tied to their parents.
Answer:
B) Some connections are lost so others can be strengthened.
Explanation:
Synaptic pruning refers to a natural process that occurs in the brain between childhood and adulthood. Extra synaptic connections are eliminated in order to increase the efficiency of neuronal communications. It is thought to be the brain’s way of removing connections that are no longer needed.