Difference between solid friction and viscosity is as follows: Viscosity is proportional to the surface area whereas solid friction is independent of area of solid surfaces in contact. Viscous force on the body depends upon its velocity in the viscous media. But, friction does not depend on the velocity of the body.
        
             
        
        
        
Answer:
3.0 cm
Explanation:
We can solve this problem by using the mirror equation:

where
f is the focal length of the mirror
p is the distance of the object from the mirror
q is the distance of the image from the mirror
In this problem we have:
f = 1.5 cm is the focal length of the mirror (positive for a concave mirror)
p = 3.0 cm is the distance of the object from the mirror
Therefore, the distance of the image is:

And the positive sign means that the image is real.
(The second part of the exercise is just the description of the image of the first exercise).
 
        
             
        
        
        
They all produce light and stuff
        
             
        
        
        
Answer:
t = 4.17 hours
Explanation:
given,
The distance between Sun and Neptune, d = 4.5 billion Km
                                                                          = 4.5 x 10⁹ Km
                                                                           = 4.5 x 10¹¹ m 
The velocity of light, c = 3 x 10⁸ m/s
The velocity is always equal to displacement by the time.
                                            <em>V = d / t    m/s</em>
∴                                           t = d / V
                                                = 4.5 x 10¹¹ m / 3 x 10⁸ m/s
                                                = 15,000 s
                                                = 4.17 h
Hence, the time taken by the light rays to reach the Neptune is, t = 4.17 h
 
        
             
        
        
        
Answer:
Speed: Distance per time, 400 km/h, and a scalar quantity.
Velocity: Displacement per time, 20 m/s south, and a vector quantity.
Explanation:
Hope this helps! Please mark as brainliest.
Thanks!