Answer:

Explanation:
information we know:
Total force: 
Weight: 
distance: 
vertical component of the force: 
-------------
In this case we need the formulas to calculate the components of the force (because to calculate the work we need the horizontal component of the force).
horizontal component: 
vertical component: 
but from the given information we know that 
so, equation these two
and 

and we know the force
, thus:

now we clear for 

the angle to the horizontal is 15.466°, with this information we can calculate the horizontal component of the force:


whith this horizontal component we calculate the work to move the crate a distance of 4 m:

the work done is W=173.48J
The volume of a warmed part of the air is reduced and its density increases.
Explanation:
In a convective form of heat transfer, the volume of a warmed part of air is not reduced and its density does not increase.
During convection, heat causes the warm part of the air to expand and its volume increases. When volume increases, density is reduced.
- Convection is a form of heat transfer that involves the actual movement of particles of the medium.
- It usually occurs in fluids i.e gases and liquids.
- In convection, the cold part exerts a buoyant force on the warmer air below and causes it to rise.
- As the warmer part is rising the cooler part replaces it and a convective cell is formed in the process.
Learn more:
Energy transfer in the sun brainly.com/question/1140127
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The branch of physics that deals with the study of force energy and motion is classic mechanics