Answer:
Height of the building = 11.4 m
Explanation:
As we know that the stone is projected at an angle 46 degree with speed 8.65 m/s
so the two components of the speed is given as
![v_x = 8.65 cos46](https://tex.z-dn.net/?f=v_x%20%3D%208.65%20cos46)
![v_x = 6 m/s](https://tex.z-dn.net/?f=v_x%20%3D%206%20m%2Fs)
vertical component of the speed is given as
![v_y = 8.65 sin46](https://tex.z-dn.net/?f=v_y%20%3D%208.65%20sin46)
![v_y = 6.22 m/s](https://tex.z-dn.net/?f=v_y%20%3D%206.22%20m%2Fs)
now we know that the ball strike at horizontal distance of 13.7 m
so we will have
![x = v_x t](https://tex.z-dn.net/?f=x%20%3D%20v_x%20t)
![13.7 = 6 t](https://tex.z-dn.net/?f=13.7%20%3D%206%20t)
![t = 2.28 s](https://tex.z-dn.net/?f=t%20%3D%202.28%20s)
now we know that in vertical direction ball will move under uniform gravity so we can use kinematics
![y = v_y t + \frac{1}{2}at^2](https://tex.z-dn.net/?f=y%20%3D%20v_y%20t%20%2B%20%5Cfrac%7B1%7D%7B2%7Dat%5E2)
![y = 6.22(2.28) - \frac{1}{2}(9.81)(2.28^2)](https://tex.z-dn.net/?f=y%20%3D%206.22%282.28%29%20-%20%5Cfrac%7B1%7D%7B2%7D%289.81%29%282.28%5E2%29)
![y = -11.4 m](https://tex.z-dn.net/?f=y%20%3D%20-11.4%20m)
Height of the building = 11.4 m
Answer:
A, B and D
2. A
Explanation:
1.Which of the following statements about light waves is true? check all correct answers
A.They come from sources across space reason is that a light can travels form its source and its moves across the space
B.They travel in a straight line from their source reason is that the type of light that undergo these is called parallel ray of light
C.They can travel through any type of material reason not all materials light can penetrate through e.g wall
D.They can be reflected by some types of material reason is that some materals reflect light rays e.g polished mirror
Complete Question
Use Stefan's law to find the intensity of the cosmic background radiation emitted by the fireball of the Big Bang at a temperature of 2.81 K. Remember that Stefan's Law gives the Power (Watts) and Intensity is Power per unit Area (W/m2).
Answer:
The intensity is
Explanation:
From the question we are told that
The temperature is ![T = 2.81 \ K](https://tex.z-dn.net/?f=T%20%3D%202.81%20%5C%20K)
Now According to Stefan's law
![Power(P) = \sigma * A * T^4](https://tex.z-dn.net/?f=Power%28P%29%20%3D%20%20%5Csigma%20%20%2A%20%20A%20%20%2A%20T%5E4)
Where
is the Stefan Boltzmann constant with value ![\sigma = 5.67*10^{-8} m^2 \cdot kg \cdot s^{-2} K^{-1}](https://tex.z-dn.net/?f=%5Csigma%20%20%3D%20%205.67%2A10%5E%7B-8%7D%20m%5E2%20%5Ccdot%20kg%20%5Ccdot%20s%5E%7B-2%7D%20K%5E%7B-1%7D)
Now the intensity of the cosmic background radiation emitted according to the unit from the question is mathematically evaluated as
![I = \frac{P}{A}](https://tex.z-dn.net/?f=I%20%20%3D%20%20%5Cfrac%7BP%7D%7BA%7D)
=> ![I = \frac{\sigma * A * T^4}{A}](https://tex.z-dn.net/?f=I%20%20%3D%20%20%5Cfrac%7B%5Csigma%20%2A%20%20A%20%20%2A%20T%5E4%7D%7BA%7D)
=> ![I = \sigma * T^4](https://tex.z-dn.net/?f=I%20%20%3D%20%20%5Csigma%20%20%2A%20%20T%5E4)
substituting values
![I = 5.67 *10^{-8} * (2.81)^4](https://tex.z-dn.net/?f=I%20%20%3D%205.67%20%2A10%5E%7B-8%7D%20%20%2A%20%20%282.81%29%5E4)
![I = 3.535 *10^{-6} \ W/m^2](https://tex.z-dn.net/?f=I%20%20%3D%203.535%20%2A10%5E%7B-6%7D%20%5C%20%20W%2Fm%5E2)
The whole of the data that you have researched on