just analyze it in this way:
20cos30*=10( radical 3 )
20sin30*=10
The gravitational potential energy:
E p = m x g x h
where m is the mass and h is the height;
m = 50 kg, g = 9.81 m/s² , h = 40 m
E p = 50 kg x 9.81 m/s² x 40 m
Answer:
E p = 19,620 J = 19.62 kJ
I can help you do them for yourself :)
Answer:
Explanation:
Since energy is conserved:
2
mu
2
=
2
mv
2
+mgh
⇒u
2
=v
2
+2gh
⇒(3)
2
=v
2
+2(9.8)(0.5−0.5cos60)
⇒v=2m/s
To solve this problem it is necessary to apply the concepts related to the Stefan-Boltzmann law which establishes that a black body emits thermal radiation with a total hemispheric emissive power (W / m²) proportional to the fourth power of its temperature.
Heat flow is obtained as follows:

Where,
F =View Factor
A = Cross sectional Area
Stefan-Boltzmann constant
T= Temperature
Our values are given as
D = 0.6m

The view factor between two coaxial parallel disks would be


Then the view factor between base to top surface of the cylinder becomes
. From the summation rule


Then the net rate of radiation heat transfer from the disks to the environment is calculated as





Therefore the rate heat radiation is 780.76W