Alift (elevator) is operated by an electric motor. it descends from the 10th floor to the 2nd floor at a constant speed. what is the main energy transformation during this journey?
gravitational potential energy → kinetic energy.
electrical energy → kinetic energy.
kinetic energy → thermal energy.
electrical energy → thermal energy.
work=force x displacement
so in order to do work, the force vector must be in the same direction as the displacement vector and the motion.
correct answers are 1.an increase or decrease in pressure 2.an increase or decrease in energy
all existing matter can undergo phase change it means they may transform from one state to another. phase change of a matter may occur due to change in energy and change in pressures.
for example there is an ice cube which is a solid and if we want to change it phase into liquid water for that purpose we have to supply some energy to ice cube it means we have to give some heat to ice cube. after supplying heat energy to the ice it will turn into water it means there is phase change from solid to liquid due to supplying the heat. similarly we can change the liquid water into solid ice cube by taking heat energy(reducing temperature) from the liquid water .
in some cases the matter doesn't want to undergo phase transformation. for example, oxygen will solidify at -361.8 degrees fahrenheit at standard pressure.but , it can change to solid state at warmer temperatures when the pressure is increased.
m = mass of the ball being raised
h = height to which the ball is raised = 0.5 m
v₀ = initial speed given to the ball = 3
v = final speed of the ball at its lowest position = ?
using conservation of energy
final kinetic energy at the lowest point = initial kinetic energy + initial potential energy
(0.5) m v² = (0.5) m v₀² + mgh
dividing each term by "m"
(0.5) v² = (0.5) v₀² + gh
inserting the values
(0.5) v² = (0.5) (3)² + (9.8) (0.5)
v = 4.34 m/s