Answer:
63.57 kg
Explanation:
weight = 140 lbs 
Let the mass  is m. 
1 lbs = 4.45 N 
The weight of an object is defined as the force with which our earth attracts the body towards its centre. 
Weight is the product of mass of the body and the acceleration due to gravity of that planet. 
W = m x g 
On earth surface g = 9.8 m/s^2 
Now convert lbs in newton 
So, 140 lbs = 140 x 4.45 = 623 N
So, m x 9.8 = 623
m = 63.57 kg
Thus, the mass is 63.57 kg.
 
        
             
        
        
        
Answer:
we go up the ramp there is a point where the beam is reflected inside the block, we carefully step back to the point where the beam is horizontal, we measure this angle which is our critical angle.
Explanation:
To design the experiment of measuring the critical angle, we describe the phenomenon, when the light passes from a medium with a higher refractive index to one with a lower index, it separates from the normal one and the Critical Angle is defined as the Angle for which the refraction occurs at 90º
             n₂ sin θ₂ = n₁ sin 90
            n₁ / n₂ = sin θ₂
As we can see, we have to measure the angle with which the laser touches the exit surface of the glass block.
Design of the experiment:
     We place the glass block on the ramp and at the top we hit the conveyor for half the angle, we climb the block on the ramp and see that the angle of incidence of lightning on the exit face changes, part of the beam comes out of the glass , we see it by dispersion in the particles of dirty in the air; Maybe the conveyor or the laser should be moved slightly so that the beam touches the point of origin on the conveyor.
    
    When we go up the ramp there is a point where the beam is reflected inside the block, we carefully step back to the point where the beam is horizontal, we measure this angle which is our critical angle.
 
        
                    
             
        
        
        
Answer:
What is the greenhouse effect?
The greenhouse effect is the way in which heat is trapped close to Earth's surface by “greenhouse gases.” 
Explanation:
These heat-trapping gases can be thought of as a blanket wrapped around Earth, keeping the planet toastier than it would be without them. Greenhouse gases include carbon dioxide, methane, nitrous oxides, and water vapor. (Water vapor, which responds physically or chemically to changes in temperature, is called a "feedback.") Scientists have determined that carbon dioxide's warming effect helps stabilize Earth's atmosphere. Remove carbon dioxide, and the terrestrial greenhouse effect would collapse. Without carbon dioxide, Earth's surface would be some 33°C (59°F) cooler.
Credit: NASA
I hope this helps, if it doesn't then just message me and ill be more than happy to help :)
 
        
             
        
        
        
Answer:
- No, this doesn't mean the electric potential equals zero.
Explanation:
In electrostatics, the electric field  is related to the gradient of the electric potential V with :
 is related to the gradient of the electric potential V with :

This means that for constant electric potential the electric field must be zero:





This is not the only case in which we would find an zero electric field, as, any scalar field with gradient zero will give an zero electric field. For example:
 
give an electric field of zero at point (0,0,0)