Answer:
1=false and 2=1st answer is correct
The effiency of a machine is
(output work or energy) / (input work or energy) .
For the system described in the question, that's
(123 J) / (150 J) = 0.82 = 82% .
Answer:
Energy absorbed or hidden when water evaporates
Explanation:
The heat that is required to make a phase change is known as latent heat.
A phase change occurs when matter changes state. For example from solid to liquid, from liquid to gas, among others.
When changing from liquid to gas (for example when water evaporates), the heat necessary for this to happen is called latent heat of vaporization. The word latent means hidden, because a change in temperature is not perceived during the phase change, even when heat is being added, thus it is said that the heat is hidden or latent.
So the answer is:
- Energy absorbed or hidden when water evaporates.
*Another type of latent heat is the latent heat of fusion, which is when a solid becomes liquid.
Frequency is no. of times this wave vibrates or complete its one cycle per unit time. As it vibrates 30000 times per second its frequency is 30000 per second or 30000 Hz [1 Hz = once per second].
