I'm pretty sure there is only one element named after Mendeleev: <span>Mendelevium.</span>
Answer:
2.068 x 10^6 m / s
Explanation:
radius, r = 5.92 x 10^-11 m
mass of electron, m = 9.1 x 10^-31 kg
charge of electron, q = 1.6 x 10^-19 C
As the electron is revolving in a circular path, it experiences a centripetal force which is balanced by the electrostatic force between the electron and the nucleus.
centripetal force = 
Electrostatic force = 
where, k be the Coulombic constant, k = 9 x 10^9 Nm^2 / C^2
So, balancing both the forces we get



v = 2.068 x 10^6 m / s
Thus, the speed of the electron is give by 2.068 x 10^6 m / s.
Spring C stretches 100 cm.
Explanation:
The spring constant is simply the stiffness of the spring. The higher the spring constant the more stiff the spring is.
Spring constant shows the force needed to stretch a spring from it's equilibrium position. If a material requires more force to cause it to stretch, it will have a high spring constant.
According to hooke's law "the force needed to extended an elastic material is directly proportional to its extension"
F = ke
k is the spring constant
e is the extension
We see that the spring that stretches by 100 is the less stiff compared to other springs. It has the smallest spring constant.
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The equation to find force is f=ma. So, if you plug in the information that you have you'll get F=5x3 and that'll equal F=15N