Some of these frictions depend on the Pressure, temperature of atmosphere.
Static Friction: This is the friction force when two objects in contact are not moving relative to each other. This friction is higher than kinetic friction.
Kinetic or Dynamic friction: this the friction force opposing the motion of objects, when two objects in contact are in motion relative to each other. It is less than the static friction. The two surfaces are rubbing against each other as they move.
Rolling friction: This is the friction when two objects are in contact and one object is rolling over the other - like a wheel on a road. The point of contact appears as stationary. The rolling friction is very less compared to static friction & dynamic friction.
Lubricated friction: this is the friction between two solid surfaces in contact with a layer of lubricant fluid flowing in between them. This friction is the least.
Fluid friction - viscosity : this is friction between two adjacent layers that are moving relative to each other at different speeds in a fluid. This is not high.
Internal friction: when an object is compressed and forced to deform, like in a piece of rubber, there is friction between the layers, that opposes this deformation.
Skin friction is the friction that opposes movement of a fluid across a solid surface. This is also called drag. When a coin is dropped in water, there is a friction called drag on the coin. Same is the case when a ball is thrown, a drag is experienced by the ball due to the drag of air.
Answer:
The radius of the cable is 0.0083 m or 8.3 mm.
Explanation:
The resistance of copper cable of 1 meter length will be given by
.... (i)
where the resistivity of copper is
, and l is the length of the wire which is considered to be 1m, and a is the cross sectional area of the wire in
.
From the formula of power we know that,
.... (ii)
Therefore 2 W/m =
.... (iii)
where the resistance,R, actually means the resistance of the cable per meter.
Therefore R ( resistance of cable per meter)
=
ohms / meter. .... (iv)
Therefore from (i)
=
..... (v)
where cross sectional area of the cable, a =
,
where r is the radius of the cable, and length of cable,l = 1m.
Therefore r = 
Answer:
A. Heat flows from an object at higher temperature to an object at lower temperature
Explanation:
The option A obeys the 2nd law of thermodynamics. The heat will flow from the object at higher temperature to the object at Lower temperature till they reach an equilibrial state.
Heat doesn’t necessarily flow from an object with higher thermal energy to an object with lower thermal energy because an object has a higher thermal energy when it’s mass is more than the other. This makes B wrong.
C is wrong because heat moves from an object with higher temperature to objects with Lower temperature regardless of the state of matter.
Answer:
100,200J of heat is required to convert 0.3kg of ice of 0°C to water at same temperature.
Explanation:
Heat = mass * lf
Latent heat of fusion (lf) of water is 334J/g
Heat = 300g * 334 J/g
Heat = 100,200J of heat
Answer:
In space we feel weightlessness because the earth's gravity has less effect on us. The Earth's gravitational attraction at those altitudes is only about 11% less than it is at the Earth's surface. If you had a ladder that could reach as high as the shuttle's orbit, your weight would be 11% less at the top.
Explanation:
Hope this helps:)