Friction occurs between two contacting surfaces. The coefficient of friction is very much dependent on the roughness of these surfaces. Some of the many ways in which the coefficient can be lessened or decreased are to lubricate the surface or make it shiny by eliminating the spikes which caused the roughness.
We can solve the problem by requiring the equilibrium of the forces and the equilibrium of torques.
1) Equilibrium of forces:

where

is the weight of the person

is the weight of the scaffold
Re-arranging, we can write the equation as

(1)
2) Equilibrium of torques:

where 3 m and 2 m are the distances of the forces from the center of mass of the scaffold.
Using

and replacing T1 with (1), we find

from which we find

And then, substituting T2 into (1), we find
Let the key is free falling, therefore from equation of motion
.
Take initial velocity, u=0, so
.

As velocity moves with constant velocity of 3.5 m/s, therefore we can use formula

From above substituting t,
.
Now substituting all the given values and g = 9.8 m/s^2, we get
.
Thus, the distance the boat was from the point of impact when the key was released is 10.60 m.
<span>The expected boiling point of a substance increases with an increasing molar mass of the substance. So I would expect the lighter compounds to boil at lower temperature. Also more polar molecules tend to boil at higher temperature.
Pentane is the lightest of all three compounds, so it should boil the soonest.
Heptane is a lot heavier than Pentane, but slightly lighter than Heptanol. So it should boil next.
Heptanol is the heaviest of all of the molecules and is also quite polar compared to heptane. So it should have the highest of all the boiling points.</span>