<u>Answer:</u> The Fermi velocity of lead is 64.4 km/s.
<u>Explanation:</u>
To calculate the Fermi velocity, we use the equation:

where,
h = Planck's constant = 
= mass of electron = 
N = Number of atoms present in per volume of atom multiplied by number of electrons present in given atom = 
= Avogadro's number =
(When the mass is in kilograms)
V = Volume = 
M = molecular weight of lead = 207.2 g/mol
Putting values in above equation, we get:

(Conversion factor: 1 km = 1000 m)
Hence, the Fermi velocity of lead is 64.4 km/s
4.0 is gonna be your answer
Answer:
5 N right
Explanation:
Fx = 9N-4N
Fx = 5N
Since we can define the x and y axis. We have x to the right as positive.
The vertical component grows at an increasing rate because
gravity is ACCELERATING the object vertically. So its speed
keeps growing. Speed is the slope of the displacement graph.
Answer:
Explanation:
My speed after the interaction will depend upon the impulse the ball will make on me . Now impulse can be expressed as follows
Impulse = change in momentum
change in momentum in the ball will be maximum when the ball bounces back with the same velocity which can be shown as follows
change in momentum = mv - ( - mv ) = 2mv
So when ball is bounced back with same velocity , it suffers greatest impulse from my hand . In return , it reacts with the same impulse on my hand pushing me with greatest impulse according to third law of motion. this maximizes my speed after the interaction.