I got E) for the first and couldn't figure out the other one. Can any one verify the first and help with the second??
In which of the following processes is there a decrease in the potential energy of the substances involved?
A) a coil spring is compressed
B) two particles of opposite charge are separated
C) photosynthesis produces glucose from carbon dioxide and water
D) liquid water evaporates to form water vapor
E) methane gas burns in oxygen to form carbon dioxide and water
The speed of light is 3.0 x 108 m/s. How many milliseconds does it take for a light signal from earth to reach and return from a satellite that is in orbit 30 miles above the earth? (1 millisecond = 10-3 seconds)
A) 320 milliseconds
B) 16 milliseconds
C) 32 milliseconds
D) 0.32 milliseconds
E) 0.16 milliseconds
To determine which processes involve a decrease in potential energy, we need to understand the concept of potential energy and how it changes in different situations.
Potential energy is the stored energy possessed by an object due to its position or condition. It can be converted into other forms of energy, such as kinetic energy. Changes in potential energy occur when an object's position or condition changes.
Let's evaluate each option to determine if potential energy decreases:
A) When a coil spring is compressed, the potential energy decreases. This is because the spring is being compressed, and the energy is transferred to other forms, such as elastic potential energy.
B) When two particles of opposite charge are separated, the potential energy increases. This is due to the electrostatic force of attraction between the opposite charges. As they are separated, work is done against this force, increasing the potential energy.
C) During photosynthesis, glucose is produced from carbon dioxide and water. This process involves the conversion of light energy into chemical potential energy, not a decrease in potential energy.
D) When liquid water evaporates to form water vapor, the potential energy increases. The water molecules gain additional kinetic energy as they transition from the liquid to the gaseous state.
E) When methane gas burns in oxygen to form carbon dioxide and water, the potential energy decreases. This is because the chemical reaction releases energy in the form of heat and light.
Therefore, the correct answer for the first question is E) methane gas burns in oxygen to form carbon dioxide and water.
Now let's move on to the second question:
To determine the time it takes for a light signal to reach and return from a satellite, we need to consider the distance and the speed of light.
The distance to the satellite is given as 30 miles above the Earth's surface. However, we need to convert this distance to meters before using the speed of light in meters per second.
1 mile is approximately 1609.34 meters, so 30 miles is 30 x 1609.34 = 48280.2 meters.
Now, we can calculate the time it takes for the light signal to travel this distance:
Time = Distance / Speed
Time = 48280.2 meters / (3.0 x 10^8 m/s)
Calculating this, we find:
Time = 0.160933 seconds
To convert seconds to milliseconds, we multiply by 1000 (since there are 1000 milliseconds in a second):
Time = 0.160933 seconds x 1000 = 160.933 milliseconds
Rounding this to the nearest whole number, the correct answer is A) 320 milliseconds.
So, the correct answers are:
- For the first question: E) methane gas burns in oxygen to form carbon dioxide and water.
- For the second question: A) 320 milliseconds.