<span>Answer:
For Lewis theory, the most stable species will have a complete octet for as many atoms as possible. Construct Lewis dot structures for each species. You should see that CN+ cannot give a complete octet to the C atom unless a quadruple bond - unknown except in transition metals - is formed. CN will have an odd number of electrons, and is thus a free radical and unstable with respect to dimerization (it forms cyanogen). CN-, the familiar cyanide ion, gives both C and N a complete octet with a triple bond, and is thus the most stable.
Molecular orbital theory is a bit more complex. Nitrogen and carbon are close enough in electronegativity, so the orbitals from the C atom will mix with the same orbitals from the N atom. The molecular orbitals formed will be sigma2s, sigma*2s, pi2p, sigma2p, pi*2p, and sigma*2p. The * denotes an antibonding orbital; these are higher in energy, and electrons placed into these orbitals weaken the bonding between two atoms. CN+ will completely fill the sigma2s, sigma*2s, and pi2p orbitals. CN will add an electron in the bonding sigma2p orbital, and the atoms are thus more strongly bonded than in CN+. CN- fills the sigma2p orbital, and the addition of another bonding electron means that this species has the strongest bond of the three. I might have the names of some of the filled levels incorrect; the energy levels of the sigma2p and pi2p swap at some point. This concept is hard to explain without a picture; see the link.
Thus, both MO and Lewis theory predict CN- as the most stable species, a prediction that matches well with experimental data.</span>
Answer:
with the mirror into the right direction
Explanation:
Answer:
a. 120 W
b. 28.8 N
Explanation:
To a good approximate, the only external force that does work on a cyclist moving on level ground is the force of air resistance. Suppose a cyclist is traveling at 15 km/h on level ground. Assume he is using 480 W of metabolic power.
a. Estimate the amount of power he uses for forward motion.
b. How much force must he exert to overcome the force of air resistance?
(a)
He is 25% efficient, therefore the cyclist will be expending 25% of his power to drive the bicycle forward
Power = efficiency X metabolic power
= 0.25 X 480
= 120 W
(b)
power if force times the velocity
P = Fv
convert 15 km/h to m/s
v = 15 kmph = 4.166 m/s
F = P/v
= 120/4.166
= 28.8 N
definition of terms
power is the rate at which work is done
force is that which changes a body's state of rest or uniform motion in a straight line
velocity is the change in displacement per unit time.
a. 850 N is the minimum force needed to get the machine/player system moving, which means this is the maximum magnitude of static friction between the system and the surface they stand on.
By Newton's second law, at the moment right before the system starts to move,
• net horizontal force
∑ F[h] = F[push] - F[s. friction] = 0
• net vertical force
∑ F[v] = F[normal] - F[weight] = 0
and we have
F[s. friction] = µ[s] F[normal]
It follows that
F[weight] = F[normal] = (850 N) / (0.67) = 1268.66 N
where F[weight] is the combined weight of the player and machine. We're given the machine's weight is 200 N, so the player weighs 1068.66 N and hence has a mass of
(1068.66 N) / g ≈ 110 kg
b. To keep the system moving at a constant speed, the second-law equations from part (a) change only slightly to
∑ F[h] = F[push] - F[k. friction] = 0
∑ F[v] = F[normal] - F[weight] = 0
so that
F[k. friction] = µ[k] F[normal] = 0.56 (1268.66 N) = 710.45 N
and so the minimum force needed to keep the system moving is
F[push] = 710.45 N ≈ 710 N
