Rate of performing work is called power.
Time = work done/Power = 1800/300 = 6 sec.
Therefore it takes 6 secs to perform work.
Answer:
Explanation:
A ball is thrown vertically upward with a certain Kinetic Energy in the absence of air resistance and while returning it experiences air resistance.
Air resistance causes the ball to lose its kinetic energy as it provides resistance which will convert some of its kinetic energy to heat energy.
So in a way total energy is conserved but not kinetic energy as some portion of it is lost in the form of heat.
The coefficient of restitution is a measure of the interaction of the ball with the material of the ground. Since the ground is too solid to move (usually), or give way, the energy of the ball-ground system must be conserved in the main. Some of the energy is released as sound waves but the rest is given to, or reflected back to the ball and it follows the path of reflection. When the ball is dropped vertically it returns along the same path. So the force is actually the potential energy created by dropping converted to kinetic energy on collision with the ground. This is the origin of the force making it bounce.
Answer:
Before giving an injection, a nurse dabs some alcohol onto the patient`s arm. This makes the patient`s skin feels cold. Explain Why ?
<em> Evaporative cooling makes this to be possible</em>
Explanation:
The concept
For a liquid to evaporate, there must be a breakdown of the bond between the molecules of the liquid. These bonds are broken when the molecules gain heat energy. So basically evaporation occurs when the molecules of the substance gain energy in form of heat.
Our Scenario
Just like the way our body excretes sweat on a sunny day, alcohol takes energy from the skin to evaporate. The bond holding the molecules of alcohol breaks faster due to its low boiling point and this account why it evaporates faster. The sudden evaporation of alcohol when dabbed on the skin results in quick utilization of heat energy making the skin feel cold for some time.
The utilization of heat energy from the skin results in evaporation cooling which makes the skin feel colder.