Factors affecting friction
The intensity of friction depends on following factors: i) The area involved in friction. ii) The pressure applied on the surfaces. Force = Pressure ´ Area Frictional force will increase, if the area of contact will increase or if pressure applied on the surface increased.
Methods to reduce friction
i) Polish the contact surface. ii) Put oil or grease so that it fills in the small gaps of the flat parts. iii) Use ball bearings to reduce area of contact between rotating parts.
Lubrication
Following methods can be used to reduce friction: Oil is either thin or viscous. It depends upon SAE No. of oil. (SAE means Society of Automotive Engineers). If we use very viscous oil, it does not reach all the parts. Very thin oil will flows away easily and gets wasted. Grease is used in such cases. It is generally used around ball-bearing. Normal grease or oil is never used where there is high pressure, high temperature and high speed. Special lubricants are used in such cases. In cold season the oil becomes thick and in hot season it becomes thin. Therefore selection of lubrication also depends on the season. It is always advisable to refer operating manual of the equipment before selecting the lubricant.
Answer:
C. Both reach the bottom at the same time.
Explanation:
For a rolling object down an inclined plane , the acceleration is given below
a = g sinθ / (1 + k² / r² )
θ is angle of inclination , k is radius of gyration , r is radius of the cylinder
For cylindrical object
k² / r² = 1/2
acceleration = g sinθ /( 1 + 1/2 )
= 2 g sinθ / 3
Since it does not depend upon either mass or radius , acceleration of both the cylinder will be equal . Hence they will reach the bottom simultaneously.
The molar latent enthalpy of boiling of iron at 3330 K is ΔH = 342 
10^3 J.
<u>Explanation:</u>
Molar enthalpy of fusion is the amount of energy needed to change one mole of a substance from the solid phase to the liquid phase at constant temperature and pressure.
d ln p = (ΔH / RT^2) dt
(1/p) dp = (ΔH / RT^2) dt
dp / dt = p (ΔH / RT^2) = 3.72 10^-3
(p) (ΔH) / (8.31) (3330)^2 = 3.72 10^-3
ΔH = 342 10^3 J.
increase the strength of the magnetic field when current flows through the circuit
She can change the arrows so they show current traveling in opposite directions on the sides of the loop.
halfway between the like poles of two magnets, because the field lines bend away and do not enter this area
A generator converts kinetic energy to electrical energy, and a motor converts electrical energy to kinetic energy.
A switch is closed, so the circuit would be complete and unbroken and the lights in the circuit would shine.
