Answer:

Explanation:
Gravitational potential energy is the energy an object possesses due to its position. It is the product of mass, height, and acceleration due to gravity.

The object has a mass of 150 kilograms and is raised to a height of 20 meters. Since this is on Earth, the acceleration due to gravity is 9.8 meters per square second.
- m= 150 kg
- g= 9.8 m/s²
- h= 20 m
Substitute the values into the formula.

Multiply the three numbers and their units together.


Convert the units.
1 kilogram meter square per second squared (1 kg *m²/s²) is equal to 1 Joule (J). Our answer of 29,400 kg*m²/s² is equal to 29,400 Joules.

The crate has <u>29,400 Joules</u> of potential energy.
Answer: If a star's radial velocity is -50 km/s, the frequency of its light would appear to be higher than its true frequency. We usually say that the star's wavelength is blue shifted.
Explanation:
Radial velocity is defined as the velocity of how an object is seen by the axis of a circle.
Then, if the radial velocity is -50km/s, this means that the radius is decreasing, and then that the star is coming towards the viewer.
as the star is coming towards the viewer, we will see a shorter wavelength, which implies that the frequency would appear to be bigger as it really is.
and this is called a blue shift, because the blue light is the visible light with the biggest frequency, while the red light is the visible light with the smallest frequency, then we have:
If a star's radial velocity is -50 km/s, the frequency of its light would appear to be higher than its true frequency. We usually say that the star's wavelength is blue shifted.